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# Lifespan Measurements in the Male Rat

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## Abstract

: Measures of lifespan were determined for a population of male Sprague-Dawley derived male rats, comprised of 747 animals from eighteen experiments. Variations in ln measures among experiments were found even under stable environmental conditions in a single strain of rats with no known epidemic infections. Measures of central tendency and dispersion appeared to be uncorrelated with each other, and normally distributed among experiments. Within most experiments there was a definite tendency for an excess (above the normal distribution) of shorter lifespans, and in seven experiments this resulted in significant deviations from the normal distribution. On a composite basis, the frequency distribution of lifespans, and the associated survival curve, were not those of a normally distributed variate. Consideration of life expectancies at various ages and age specific death rates revealed that the force of mortality declines at advanced ages. These findings indicate the need for caution in selecting statistical procedures for analysis of lifespan information.

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... The SO and SG groups had free access to the high-fat diet for 6 weeks after surgery. This schedule was planned based on the Sprague-Dawley rat's lifespan of less than 2 years and stable fecundity of 8 to 20 weeks [18]. The amount of food in the PF group was adjusted ad lib to the weekly intake observed in the SG group as previously described [19]. ...
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Background: Short-chain fatty acids (SCFAs) and gut microbiota have health-related effects and are associated with a wide range of disorders. However, the changes of SCFAs and their receptors after sleeve gastrectomy (SG) remain unclear. This study aimed to examine changes of SCFAs and their receptors after SG in an obese rat model. Methods: Thirty obese Sprague-Dawley rats eating a high-energy diet for 6 weeks were divided into three groups: sham-operated (SO) control, pair-fed (PF) control, and SG group. Six weeks after the surgery, metabolic parameters, SCFA levels in the blood and stool, mRNA and protein expression of SCFA receptors in the ileum and epididymal fat, and gut microbiota were examined. Results: Metabolic parameters in the SG group were significantly improved compared with the SO group. Acetic acid levels in the blood and stool were significantly higher in the SG group than the PF group. The butyric acid level in the stool was also significantly higher in the SG group than in the PF group. In the ileum and epididymal fat, mRNA and protein expression of GPR41 was significantly higher in the SG group than in the other two groups, and mRNA and protein expression of GPR43 was significantly higher in the SG group than in the PF group. Increases in the genera Enterococcus, Lactobacillus, Lactococcus, and Clostridium were observed in the stool after SG. Conclusions: SG may activate SCFA pathways through a change in gut microbiota.
... Although the long median life span of our control rats may be inherent in the strain, the ages of the last survivors did not differ from those reported for Sprague-Dawley males by Berg and Harmison (22) (21) for Holtzman rats, about 670 days, ages similar to those of our lead-fed males, 729 days. The median life spans of our control and chromium-fed animals were 7 to 9 months longer, and their normal sigmoid-shaped curves fell sharply at a considerably later interval than did those published by Jones and Kimeldorf (24) and McCay et al. (18), resembling rats restricted as to food (17,18,20). There fore, these Long-Evans rats did not differ from other common strains in maximal longevity, but under the conditions of this experiment could be made to shorten their median life span according to the intake of 2 extraneous trace elements, cadmium and lead, and to lengthen them by restric tion of these elements, even when fed ad libitum. ...
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... In addition, they were subjected to intermittent (6 months intervals) measurements in psychological, metabolic, or physical fitness tests. These tests, as well as details of animal maintenance, have been described previously (9). No epidemic respiratory pathology was observed throughout the course of this study. ...
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David B. Duncan [2] has formulated a new multiple range test making use of special protection levels based upon degrees of freedom. Duncan [Tables II and III] has also tabulated the critical values (significant studentized ranges) for 5 percent and 1 percent level new multiple range tests, based upon tables by Pearson and Hartley [8] and by Beyer [1]. Unfortunately, there are sizable errors in some of the published critical values. This fact was discovered and reported by the author [4], who instigated the computation at Wright-Patterson Air Force Base of more accurate tables of the probability integrals of the range and of the studentized range than those published by Pearson and Hartley [7, 8]. This extensive computing project, of which one of the primary objectives was the determination of more accurate critical values for Duncan's test, has now been completed. The purpose of this paper is to report critical values (to four significant figures) which have been found by inverse interpolation in the new table of the probability integral of the studentized range. Included are corrected tables for significance levels α = 0.05, 0.01 and new tables for significance levels α = 0.10, 0.005, 0.001-all with sample sizes n = 2(1)20(2)40(10)100 and degrees of freedom ν = 1(1)20, 24, 30, 40, 60, 120, ∞.
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