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Biomedical subjects

J M Lyons

Publications and source records attributed to J M Lyons.

At least 55 records · Page 3Linked to original sources
PubMed1974

Effect of chilling temperatures on the activities of glyoxysomal and mitochondrial enzymes from castor bean seedlings.

Castor bean (Ricinus communis L.) is included among the group of plants sensitive to chilling temperatures. Seedlings of this species were shown to exhibit visible symptoms of this injury, as well as impaired radicle growth and storage product mobilization. Respiration of intact seedlings and oxidation of succinate by isolated mitochondria displayed discontinuities in Arrhenius plots of their reaction velocities, characteristic of chilling species. However, gluconeogenic glyoxysomal enzymes do not display such discontinuities, indicating that there is probably no functional relationship between these enzymes and the glyoxysomal membrane.

Journal Article↗
PubMed1974

Immunization against retrograde pyelonephritis. I. Production of an experimental model of severe ascending Escherichia coli pyelonephritis without bacteremia in rats.

Retrograde pyelonephritis was produced in rats by introducing into the bladder a small refluxing inoculum of Escherichia coli that would enter the renal pelvis but not the blood stream. At the same time the left ureter was partially obstructed for 18 hours. This model differs from previous attempts to produce E coli pyelonephritis with large (0.6 ml) volumes infused into the bladder, because such large volumes cause bacteremia and hematogeneous pyelonephritis. Since retrograde E coli pyelonephritis in patients is not accompanied by positive blood cultures, the model described in this report is believed to accurately mimic human pyelonephritis and to allow a realistic approach to the study of immunity against retrograde infection in the urinary tract.

Animals↗
PubMed1974

Immunization against retrograde pyelonephritis. II. Prevention of retrograde Escherichia coli pyelonephritis with vaccines.

Vaccination with heat-killed or formalinized cells of E coli 0:111, or E coli 06 (Williams), prevented retrograde E coli pyelonephritis. Since there was no bacteremia and no urinary antibody, the vaccination appeared to protect by immune reactions operating in the kidney itself. The vaccine failed to protect against a highly virulent form of E coli 06 (Riffle), possibly because the amount of antibody to its lipopolysaccharide was inadequate. Since all three strains possessed K antigen in approximately equal amounts, the difference in results was not attributed to its presence.

Animals↗
PubMed1971

Hibernation: alteration of mitochondrial membranes as a requisite for metabolism at low temperature.

Lipids of mitochondrial membranes from hepatic cells of active ground squirrels apparently go through a phase change induced at approximately 23 degrees C similar to the phase change in mitochondria of homeotherms. This change was indicated by the activity of succinate oxidase from the isolated mitochondria exhibiting a nonintersecting discontinuous Arrhenius plot. This discontinuity in the Arrhenius plot is not evident with mitochondria from the livers of hibernating squirrels, which indicates that the temperature-induced phase change in the mitochondrial membranes has been eliminated. These findings suggest that physical properties of the mitochondrial membrane change in relation to the process of hibernation.

Adenosine Diphosphate↗
PubMed1970

The influence of mitochondrial concentration and storage on the respiratory control of isolated plant mitochondria.

The respiration of mitochondria isolated from various plant tissues was studied over a range of mitochondrial concentrations and at various times after isolation. Respiration at 25 C expressed as nanomoles of O(2) per minute per milligram of protein was constant for mitochondrial concentrations higher than some critical amount, usually 0.25 to 1.0 milligram of protein per reaction. Below this concentration the state 3 respiration rate declined and the mitochondria appeared to lose respiratory control. The respiration of isolated mitochondria stored in ice but measured at 25 C generally declined over long time periods although mitochondria from some tissues showed an initial increase. The results indicate that valid comparisons of the respiratory activity of mitochondria isolated from different tissues or from different parts of the same tissue cannot be made at least until the influence of the above factors has been evaluated.

Adenine Nucleotides↗
PubMed1970

Oxidative activity of mitochondria isolated from plant tissues sensitive and resistant to chilling injury.

Arrhenius plots of the respiration rates of mitochondria isolated from chilling sensitive plant tissues (tomato and cucumber fruit, and sweet potato roots) showed a linear decrease from 25 C to about 9 to 12 C (with Q(10) values of 1.3 to 1.6), at which point there was a marked deviation with an increased slope as temperatures were reduced to 1.5 C (Q(10) of 2.2 to 6.3). The log of the respiration rate of mitochondria from chilling resistant tissues (cauliflower buds, potato tubers, and beet roots) showed a linear decrease over the entire temperature range from 25 to 1.5 C with Q(10) values of 1.7 to 1.8. Phosphorylative efficiency of mitochondria from all the tissues, as measured by ADP:O and respiratory control ratios, was not influenced by temperatures from 25 to 1.5 C. These results indicate that an immediate response of sensitive plant tissues to temperatures in the chilling range (0 to 10 C) is to depress mitochondrial respiration to an extent greater than that predicted from Q(10) values measured above 10 C. The results are also consistent with the hypothesis that a phase change occurs in the mitochondrial membrane as the result of a physical effect of temperature on some membrane component such as membrane lipids.

Adenine Nucleotides↗
PubMed1970

A Lack of Specificity for Ethylene-induced Mitochondrial Changes.

A critical evaluation was made of the hypothesis that the primary mode of action of ethylene in inducing physiological responses is by changing the permeability of cell organelles. The parameter investigated was the evaluation of the influence of ethylene and other gases on mitochondrial oxidation and swelling. Spectrometric evidence demonstrated that mitochondria prepared with good respiratory control can be induced to swell more rapidly with ethylene and other aliphatic gases (ethane, propene, propane, I-butene) in test solutions of 0.125 m KCl. The fact that saturated as well as unsaturated hydrocarbon gases elicited similar changes provides evidence that ethylene does not directly alter membrane permeability as its mechanism of action.

Journal Article↗
PubMed1970

Sex expression in cucumber plants as affected by 2-chloroethylphosphonic Acid, ethylene, and growth regulators.

The effects of 2-chloroethylphosphonic acid (Ethrel), ethylene, and some growth retardants on sex expression of cucumber plants (Cucumis sativus L.) were investigated, with the use of a monoecious cultivar (Improved Long Green) which has a strong tendency toward maleness.Ethrel caused increased femaleness when applied at 50 milligrams per liter at the first to the third leaf stage, but when applied at the cotyledon stage it was ineffective. The later the time of application, the higher the node at which the first female flower appeared. The total number of female flowers was about the same regardless of application time. A mixture of gibberellins A(4) and A(7) caused maleness, and Ethrel caused femaleness. However, when applied in combination at the first leaf stage the interaction was not significant. It seems, therefore, that Ethrel and gibberellins are not antagonistic but rather have different sites of action, although they have opposing effects on sex expression.Ethylene caused femaleness but was far less effective than Ethrel. Alar (N-dimethylaminosuccinamic acid), CCC((2-chloroethyl)trimethylammonium chloride), Phosphon D(2, 4-dichlorobenzyl-tributylphosphonium chloride), and abscisic acid did not affect sex expression of cucumber.

Journal Article↗