Effects of 48 F. (8.9 C.) and 83 F. (28.4 C.) on Longevity and Pathology of Male Rats

Johnson, H. D.; Kintner, Loren D.; Kibler, H. H.

doi:10.1093/geronj/18.1.29

Cited by 35 publications

(8 citation statements)

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“…The range so determined of 17.4 g/cm2 corresponds to 160 MeV, (12) which is in agreement with other reported values of 159 MeV, (16) 157 MeV(@ and 160.5 MeV. (17) With the phantom positioned -55' from the beam axis, no primary (beam) protons can reach it except possibly by scattering. The absorbed dose as a Phantom of beam axis.…”

Section: High-energy Proton Experimentssupporting

confidence: 90%

The Energy Deposition in a Water-filled Spherical Phantom by Secondaries from High-energy Protons and by Neutrons

Blosser¹,

Maienschein²,

Freestone³

1964

Health Physics

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The energy deposited by neutrons, gamma rays, high-energy protons, and the nuclear secondaries resulting from the interaction of high-energy protons with several targets has been measured a t various points within a 42-cm-diameter spherical water-filled Lucite phantom. The proton source was the Harvard University Synchrocyclotron, producing protons of nominally 160-MeV energy. Targets were water, aluminum, carbon, copper and bismuth. For neutrons the H3(d, n)He4 reaction, giving -14.9-MeV neutrons, and a Po-Be source (& = 4.3 MeV) were used. The gamma-ray source was Co60. The detectors were small Lucite-walled ionization chambers filled with either ethylene or 97% Ar-3% CO, gas.Data were taken at the cyclotron both with the phantom on the beam axis and with the phantom offset -55" from the beam axis. The proton beam energy determined from a part of these results, -160 MeV, is in good agreement with published values. The energy deposited by secondary particles was found to increase with target-atomic number, as expected. The depth-dose curves have a steeply negative slope over the region near the surface of the phantom and a more gentle slope at greater depths. The magnitude of the dose in the region of the initial slope decreases with increasing target thickness, while the magnitude of the dose at greater depths increases with increasing target thickness. The dose in the region of initial slope is presumably due to secondary protons, while at greater depths the dose is principally controlled by secondary-neutron interactions.With an aluminum target thicker than the incident proton range, the absorbed dose a t -55" from the beam axis was only about 20 per cent of that at 0". Comparison of the slopes of the depth dose due to the secondaries (assumed to be largely neutrons) from this target with the slopes obtained with the neutron sources suggests that the effective energy of the secondaries is greater than 15 MeV.These experimental data were obtained to permit detailed comparisons with calculations of the physical dose due to secondaries from high-energy protons. The results of such calculations are not yet available. nuclear secondaries (neutrons, protons and gamma rays) resulting from the interaction of phantom by protons, second-of interest. Such data are needed to assess the aries from the interaction of these protons with validity of the Monte Carlo transport calcugamma rays has been physical dose due to the interaction of solar protons with spacecraft shields. Since calcuinferred from ionization measurements made as

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Section: High-energy Proton Experimentssupporting

confidence: 90%

The Energy Deposition in a Water-filled Spherical Phantom by Secondaries from High-energy Protons and by Neutrons

Blosser¹,

Maienschein²,

Freestone³

1964

Health Physics

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“…Kibler and lohnson (1961;Johnson et al 1963;Kibler et al 1963) have shown that rats kept at 9°C continuously had shorter life spans than rats at 28°C, and these studies have been cited as providing experimental support for the rate-of-living theory. Holloszy and Smith (1986) argued that the continuous cold exposure in lohnson et al's (1963) study was a chronic Stressor.…”

Section: Discussionmentioning

confidence: 99%

Metabolism and Aging: Effects of Cold Exposure on Metabolic Rate, Body Composition, and Longevity in Mice

Vaanholt¹,

Daan²,

Schubert³

et al. 2009

Physiological and Biochemical Zoology

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The proposition that increased energy expenditure shortens life has a long history. The rate-of-living theory (Pearl 1928 ) states that life span and average mass-specific metabolic rate are inversely proportional. Originally based on interspecific allometric comparisons between species of mammals, the theory was later rejected on the basis of comparisons between taxa (e.g., birds have higher metabolic rates than mammals of the same size and yet live longer). It has rarely been experimentally tested within species. Here, we investigated the effects of increased energy expenditure, induced by cold exposure, on longevity in mice. Longevity was measured in groups of 60 male mice maintained at either 22 degrees C (WW) or 10 degrees C (CC) throughout adult life. Forty additional mice were maintained at both of these temperatures to determine metabolic rate (by stable isotope turnover, gas exchange, and food intake) as well as the mass of body and organs of subsets of animals at four different ages. Because energy expenditure might affect longevity by either accumulating damage or by instantaneously affecting mortality rate, we included a third group of mice exposed to 10 degrees C early in life and to 22 degrees C afterward (CW). Exposure to cold increased mean daily energy expenditure by ca. 48% (from 47.8 kJ d(-1) in WW to 70.6 kJ d(-1) in CC mice, with CW intermediate at 59.9 kJ d(-1)). However, we observed no significant differences in median life span among the groups (WW, 832 d; CC, 834 d; CW, 751 d). CC mice had reduced body mass (lifetime mean 30.7 g) compared with WW mice (33.8 g), and hence their lifetime energy potential (LEP) per gram whole-body mass had an even larger excess than per individual. Greenberg ( 1999 ) has pointed out that the size of the energetically costly organs, rather than that of the whole body, may be relevant for the rate-of-living idea. We therefore expressed LEP also in terms of energy expenditure per gram dry lean mass or per gram "metabolic" organ mass (i.e., heart, liver, kidneys, and brain). No matter how it was expressed, LEP in CC mice significantly exceeded that of WW mice. This result demonstrates that increased energy expenditure does not shorten life span and adds evidence to the intraspecific refutation of the rate-of-living theory. We suggest that increased energy expenditure has both positive and negative effects on different factors determining life span and that the relationship between energy turnover and longevity is fundamentally nonmonotonic.

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“…Because dpJdh is known and driir/dH can be measured, (33) represents a linear integral equation of first kind for the desired anisotropy field distribution f. In [6], Ha distributions are determined numerically. Here, the problem is treated analytically in the simplest way by starting from (33).…”

Section: Fig 3 Coercivity Vs Particle Volume (Solid Line Accordingmentioning

confidence: 99%

Determination of anisotropy field distribution in particle assemblies taking into account thermal fluctuations

Pfeiffer

1990

phys. stat. sol. (a)

284

134

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The anisotropy field distribution in assemblies of single domain particles is calculated from remanence curves. Thermal fluctuations are taken into account which are essential for particle volumes approaching the superparamagnetic critical volume. The calculations are carried out for aligned and randomly oriented assemblies. Using these results the temperature dependence of the mean anisotropy field is determined and simple expressions for the variation of the coercivity with the particle volume are given. The influence of the anisotropy field distribution and the particle–particle interaction on the magnetic properties of the assembly is discussed.

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Effects of 48 F. (8.9 C.) and 83 F. (28.4 C.) on Longevity and Pathology of Male Rats

Cited by 35 publications

References 0 publications

The Energy Deposition in a Water-filled Spherical Phantom by Secondaries from High-energy Protons and by Neutrons

The Energy Deposition in a Water-filled Spherical Phantom by Secondaries from High-energy Protons and by Neutrons

Metabolism and Aging: Effects of Cold Exposure on Metabolic Rate, Body Composition, and Longevity in Mice

Determination of anisotropy field distribution in particle assemblies taking into account thermal fluctuations

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