Article

Lifespan Measurements in the Male Rat

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

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.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... 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]. ...
Article
Full-text available
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. ...
Article
Groups of 50 or more Long-Evans rats in a low metal environment and fed a diet devoid of cadmium and low in many trace metals were given 5 ppm chromium (III), cadmium or lead in drinking water from weaning until death. Life span was shortened in those fed lead and cadmium; tissue concentrations were within human ranges. Longevity of the last 10% was increased in those fed chromium; tissue concentrations were within ranges of young human beings, and females resisted an epidemic of pneumonia. Rats fed lead had fewer tumors than controls or other groups. Arteriolar sclerosis in kidneys and ventricular hypertrophy occurred largely in cadmium-fed animals; cirrhosis of the liver in all groups. Organs of controls were cadmium-free; the metal occurred in animals from another laboratory. Cadmium did not accumulate in kidneys at older ages. Older rats fed lead showed less in organs than younger ones. Chromium did not accumulate in tissues. Extension of life span by restriction of food was reproduced by restriction of lead and cadmium and feeding of chromium. Results indicate that lead and cadmium at human tissue concentrations are toxic to rats in terms of life span and longevity, whereas chromium (III) is not.
... 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. ...
Article
The Journal of Investigative Dermatology publishes basic and clinical research in cutaneous biology and skin disease.
Article
Male and female rats were fed 40% of calories as beef tallow (BT) (polyunsaturated to saturated (P:S) fatty acid ratio = 0.17) or a mix of safflower oil and beef tallow to give a P:S of 0.94 (M) in a nutritionally complete diet. Groups were killed at 9, 12, 15, 18, and 21 months of age and fatty acid and cholesterol concentration and synthesis in liver in vivo were measured. Serum cholesterol concentration and appearance of newly synthesized lipid were also determined. Serum cholesterol concentration increased with age regardless of diet. Fatty acid synthesis from alanine was generally similar to that reported for acetate in response to variables, being higher in females than males and in males consuming BT diet than those consuming M diet. Cholesterol synthesis from alanine was similar to that reported from acetate with regard to sex effect (females higher than males), but did not differ in response to diet. The latter is contrary to reports for acetate incorporation, which has been higher for more polyunsaturated dietary fats. Female rats exhibited very high rates of incorporation of alanine into both fatty acids and cholesterol at 12–18 months of age when they were fed beef tallow. This effect was not observed in females fed mixed fat nor in males. The 21 month old BT females had alanine incorporation rates more like the rats at early ages. This decline at advanced age may be the result of death of those with high synthesis rates and survival of those with lower rates.
Article
The effects of the population density on growth and life span of 21 to 26 months in SD-JCL-rats were investigated. The mean life spans of males and females were 23 and 24 months, respectively. The population density had no definite influence on increase in body weight of females, whereas a most accelerated growth of males was seen with 2 rats per cage. The total amounts of food intake of each animal throughout its life were about 15 and 11 kg for males and females, respectively, and those of water intake were about twice the food. No correlation was observed between the population density and the weights of the liver, kidney, heart and femur, though mals reared at 5 animals per cage had lightest adrenals among all the animals.
Article
Hemodynamic and metabolic effects of three times 4 min of oxygen deficiency were investigated in 18-month-old rats in comparison to 4-month-old Wistar rats. Left-ventricular isovolumicpressure-generating capacity and dp/dtmax during isovolumic conditions and hemodynamic indices during intact circulation were determined in open-chest rats. Additionally, high-energy phosphates were measured at the end of the experiments after 20 min of postasphyxial recovery. Older rats had a significantly reduced isovolumic left-ventricular pressure generating capacity (236±9 vs 269±5 mm Hg; p<0.05) and a low cardiac index (55±9 vs 117±8 ml×min−1×kg−1). The effects of the oxygen deficiency were comparable in both groups. The isovolumic pressure generating capacity was reduced for 11% vs 14%, and dp/dtmax for 13% vs 13%. The myocardial ATP-content was also decreased for the same extent in both groups (0.6 vs 1.0 μmol/gww). Both hemodynamic and biochemical results indicate that aged myocardium does not have a reduced tolerance to repeated periods of oxygen deficiency.
Article
Experimental aging research is very dependent on the determination of the survival characteristics of the animal species or strain under study. Such data are generally inferred from mortality curves of cohorts of animals that are set aside at an early age for aging studies. Rectangular survival curves and the presence of multiple pathological lesions are a prerequisite for aging studies so as to resemble the situation in man. From 1977 onwards, many rat cohorts have been formed in the Institute for Experimental Gerontology (IVEG) for the study of aging processes. Data from these have been analysed for a period of 5 years up to and including 1982. (Males and females of the WAG/Rij and BN/BiRij strains were used.) The 50% survival and the maximum survival of cohorts varied considerably, but showed no consistent trend over the years. The median (50%) survival between the cohorts differed by as much as 7.9-10.7 months for the strains and sexes studied. Maximum survival between the cohorts varied from 3.7 to 9.9 months. Median and maximal survival were greater for the females. Maximum survival and 50% survival correlated significantly, the relation between the two being approximately linear. The effect of removing animals from cohorts on the estimation of 50% survival was only minor, whereas maximum survival was clearly diminished by this procedure. The wide variation in survival characteristics, even between successive cohorts, cautions against too simple a measure of the animals survival in only one number for median or maximal survival in months. An indication of the variance of 50% survival and of maximum survival should therefore be included in scientific publications. Moreover, the 50% survival is the parameter of choice to define cohorts, not only because this can be most reliably estimated with good confidence limits, but also because this measure is the least sensitive to removing animals from the cohorts. As this will often be the case in many research institutions, it might be of practical importance to order old animals from different cohorts since this diminishes the chance of using an extremely short or long lived cohort. Finally, the analysis revealed that combining intact or incomplete cohorts into larger survival curves resulted in nearly identical graphs. An attempt was made to calculate the minimum cohort size which yields survival curves with constant 95% confidence limits.
Article
Male rats of 90, 150, 300, 450 or 600 days of age were placed into sedentary or physical training experimental groups. Experimental animals ran daily for 20 min at 10–20 m/min on a treadmill set at an 8-degree incline. The experimental period lasted at least 300 days. Surviving rats from each group were chosen randomly and sacrificed at 150-day intervals up to 1,050 days of age. Muscle and organ weights were analyzed by grouping animals according to their age at death and also according to their age at the initiation of the training program. Muscle and organ weight data suggest that training has a minimal affect on rats past a threshold age (approximately 450 days of age), and initiation of a training program at a late age (approximately 600 days of age) may adversely affect the rat. When the effects of age and training are combined, those attributable to age seem to be more important, supporting the view that there is a threshold age beyond which the initiation of a training program no longer affects the muscle and organ weights.Copyright © 1974 S. Karger AG, Basel
Article
In a duration-of-life study, male Sprague-Dawley rats were exposed to 220 rads of fast neutrons as juveniles (1 month of age), young adults (3 months), middle-aged adults (10, 15 months), or old adults (21 months) and compared with their sham-irradiated littermates at intervals using a variety of criteria of radiation injury. In all five age groups, there was a deficit in body weight that persisted throughout life. The magnitude of this deficit was inversely related to age at exposure. Decreased food and water consumption were seen throughout life in the group irradiated as juveniles and, to a lesser extent, after exposure as young or middle-aged adults. These consummatory changes appeared related to the changes in body size. An age-associated marked increase in water consumption per unit metabolic size occurred earlier (than in controls) in animals exposed as juveniles or as young adults. Proportions of exposed groups with one or more palpable tumors were in excess of control values after exposure at all except the oldest age in spite of significant life-shortening after exposure at the three younger ages. Proportions of irradiated groups with palpable growths of large size (2.5 cm or more) exceeded those for controls even for the group exposed at 21 months.
Article
Male rats received whole-body single doses of 250-kVp x-rays at various ages ranging from young adulthood to old age. From probit analysis, the ${\rm LD}_{50(30)}$ values for groups exposed at 3 or 7 months of age were 851 and 900 R, respectively. After adjustment for the natural mortality rate, ${\rm LD}_{50(30)}$ values for groups exposed at 17, 21, or 24 months of age were 776, 806, and 747 R, respectively. The mean survival time at the ${\rm LD}_{50(30)}$ for the group exposed at 3 months of age exceeded those for groups irradiated at older ages. The slope of the dose versus survival curve for the youngest group was almost twice that for groups exposed at older ages, reflecting increased variability of the population at older ages. These findings indicate that age at exposure is an important variable to be considered in establishing parameters of acute radiation mortality in adult animals.
Article
Male-Sprague-Dawley rats (CrL:CD(SD)BR) were maintained under barrier conditions at Charles River Breeding Laboratories (Wilmington MA) from August, 1975, to July, 1983. Animals were provided food and water ad libitum. Survival data from 8 completed cohorts of 100 animals each and one continuing cohort reveal a highly significant linear increase in median lifespan, yielding a 26% increase in this parameter for cohorts born over a period of less than six years. The biological factors responsible for this increase are not clear at present. Nevertheless, these results in outbred rats, taken in conjunction with previous observations of a trend towards increased longevity in inbred mice, indicate that the assumption of cohort equivalence underlying many cross-sectional studies of biological aging may not be valid.
Article
Regional cerebral metabolic rates for glucose (rCMRglc) were studied in unanesthetized Beagle dogs in five age groups. Significant age-related differences did not occur in the cingulate, pyriform or visual cortices, cerebellar flocculus, corpus callosum, or cerebellar white matter. However, age-related decrements were apparent in 15 of the 22 brain regions examined. The apparent time course of age effect on rCMRglc varied among the brain regions. Most regions had significantly lower rCMRglc at 6 years than at 1 year. Decrements of more than 25% were seen in the mammillary bodies, pons, hippocampus, superior colliculus, basis of the midbrain, temporal cortex, geniculate bodies, caudate nucleus, and superior frontal gyrus. There were no age differences in rCMRglc at 10-12 years compared with 6 years. Senescence-associated decrements (after 6 years) were noted in only 5 regions: the frontal and temporal cortices, mammillary bodies, and areas involved in sensory functions. The results indicate that rCMRglc in the adult Beagle brain declines by midlife, and continues to decline in some brain regions through senescence.
Article
The reduction of life span by a single exposure to ionizing radiation, with displacement of the normal pattern of neoplastic and degenerative diseases toward higher incidences at younger chronologic ages, is well known. Although the relative displacement and importance of these diseases as causes of death are still matters requiring further study, many investigators find it useful to regard radiation as having an "aging" effect. Evaluation of this concept has led to the realization that the age at exposure has an effect on the degree of life shortening. Unfortunately, there have been few reports in which large numbers of animals have been irradiated at various ages distributed over an extensive proportion of the normal life span. In a recent review of the literature with respect to reduction of life span as a function of age of X-irradiation for mice, Kohn and Guttman (1) concluded that, in general, irradiation of old adults tends to have less life-shortening effect than irradiation of young adults, although the difference is not the same among several strains. For the rat, there is no corresponding body of data in the literature. In designing the present study it was felt that the information most pertinent to the role of age at irradiation could be obtained by maximizing the number of animals and the range of ages at exposure while restricting radiation to a single dose. To this
Article
Groups of 50 or more Long-Evans rats in a low metal environment and fed a diet devoid of cadmium and low in many trace metals were given 5 ppm chromium (III), cadmium or lead in drinking water from weaning until death. Life span was shortened in those fed lead and cadmium; tissue concentrations were within human ranges. Longevity of the last 10% was increased in those fed chromium; tissue concentrations were within ranges of young human beings, and females resisted an epidemic of pneumonia. Rats fed lead had fewer tumors than controls or other groups. Arteriolar sclerosis in kidneys and ventricular hypertrophy occurred largely in cadmium-fed animals; cirrhosis of the liver in all groups. Organs of controls were cadmium-free; the metal occurred in animals from another laboratory. Cadmium did not accumulate in kidneys at older ages. Older rats fed lead showed less in organs than younger ones. Chromium did not accumulate in tissues. Extension of life span by restriction of food was reproduced by restriction of lead and cadmium and feeding of chromium. Results indicate that lead and cadmium at human tissue concentrations are toxic to rats in terms of life span and longevity, whereas chromium (III) is not.
Article
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, ∞.
Note on some mathematical mortality models
  • R E Board
Board, R. E.: Note on some mathematical mortality models. Int G. E.
Actuarial aspects of human life spans
  • B Benjamin
Benjamin, B.: Actuarial aspects of human life spans. In: G. E.
Ciba Foundation colloquia on ageing The lifespan of animals. Little
  • M O Woistenholme
  • Connor
Woistenholme and M. O'Connor (Editors), Ciba Foundation colloquia on ageing. Vol. 5: The lifespan of animals. Little, Brown and Co., Boston, Mass., 1959, pp 2-20.
The lifespan of animals
  • F Verzar
Verzar, F.: In: G. E. Woistenhol.me and M. O'Connor (Diitors), Ciba Foundation Colloquia on ageing. Vol. 5: The lifespan of animals.