Alterations in endogenous circadian rhythm of core  temperature in senescent Fischer 344 rats

McDonald, Roger B.; Hoban-Higgins, T. M.; Ruhe, Rodney C.; Fuller, Charles A.; Horwitz, Barbara A

doi:10.1152/ajpregu.1999.276.3.r824

Cited by 19 publications

(18 citation statements)

References 24 publications

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“…The terminal weight loss in our rats did not relate to specific pathologies, which is in agreement with the findings of McDonald et al (21). For the DR rats, the pattern of differences in food intake and weight loss (Table 3) between pathology classifications (renal 1-3, nonneoplasm vs. renal 1-3, neoplasm) was consistent with weight loss being associated with reduced food intake.…”

Section: Discussionsupporting

confidence: 92%

“…McDonald and associates (21) suggested that the physiological decline occurring in senescent F344 rats is similar to the geriatric failure to thrive syndrome in humans. In humans, a decline in appetite and food intake with age, termed the anorexia of aging, is thought to predispose elderly individuals to the unintentional weight loss and malnutrition that are hallmarks of the failure to thrive syndrome (7,11).…”

Section: Discussionmentioning

confidence: 98%

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Senescent terminal weight loss in the male F344 rat

Black¹,

McMahan²,

Masoro

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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. Senescent terminal weight loss in the male F344 rat. Am J Physiol Regul Integr Comp Physiol 284: R336-R342, 2003. First published October 17, 2002 10.1152/ajpregu.00640.2001.-Loss of weight, often of unknown cause and culminating in death, commonly occurs in humans at advanced ages. Rats that live to old ages, such as the Fischer 344 (F344) strain, also exhibit a terminal loss in body weight. A presently held hypothesis is that the terminal weight loss in the F344 rat model is due to reduced food intake because of an alteration in hypothalamic function resulting in early satiation. We report findings on terminal weight loss and food intake in male F344 rats fed ad libitum (AL group) or a life-prolonging dietary regimen in which caloric intake was restricted (DR group). Rats in both dietary groups that did not exhibit a terminal weight loss died at younger ages than those exhibiting the loss. Terminal weight loss in the AL group was not associated with decreased food intake; indeed, half of the rats in this group had an increased food intake during the period of terminal weight loss. This finding is not in accord with the presently held hypothesis. In the DR group, terminal weight loss was associated with reduced food intake. Pathology (renal disease and neoplasms) did not explain the presence or absence of the association between reduced food intake and weight loss in either dietary group. The duration of the period of terminal weight loss was similar for the AL and DR groups. Apparently, restricting calories delays the occurrence but does not affect the duration of senescent terminal weight loss. caloric restriction; food intake; hypothalamic function LOSS OF WEIGHT CULMINATING in death commonly occurs in humans at advanced ages and is a hallmark of a geriatric syndrome termed failure to thrive (11). Although in some individuals the loss in body weight is due to age-associated disease, the cause of this weight loss in many elderly individuals is unknown (28).Most rats that live to old ages also exhibit a terminal loss in body weight (5, 27, 33). Blanton et al. (4) proposed that the Fischer 344 (F344) rat is a good animal model for the study of the physiological basis of senescent terminal weight loss. They found the loss of weight to be associated with a decrease in food intake related to the consumption of shorter and smaller meals, rather than a decreased number of daily meals (5). These investigators hypothesized that senescent terminal weight loss is caused by neurochemical alterations in the hypothalamus resulting in dysregulation of food intake relative to the organism's energy needs (4).Since 1975, our laboratory has carried out life span studies on male F344 rats, and it was our impression that senescent weight loss often was not associated with decreased food intake. In the present study we have investigated this issue in three groups of rats studied in the 1980s and early 1990s for which detailed data are available on body weight, food intake throughout the life span, and pathological lesions at t...

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 98%

Senescent terminal weight loss in the male F344 rat

Black¹,

McMahan²,

Masoro

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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“…In fact, the difference between aging and senescence needs to be taken into account, since major changes in Tc rhythms observed in aged animals under thermoneutrality (25°C) seem to appear with the first signs of senescence, as demonstrated in rats (26). Although age-related deficits in thermoregulation were not consistently demonstrated in both humans and nonhumans in the past, recent studies corroborate the fact that some subtle age-associated changes in thermoregulatory responses can be seen, even under a mild cooling condition (10) and can be influenced by external factors such as the photoperiod (5).…”

Section: Discussionmentioning

confidence: 99%

“…16), but experimental data on this matter are not always consistent. For example, in aged rats (26), mean body temperature levels do not differ significantly between young and aged rats, but age-related differences can be observed in regard to changes in amplitude of the daily body temperature rhythm. In fact, mean body temperature levels show significant decrease in senescent rats only.…”

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confidence: 96%

Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus

Terrien¹,

Zizzari²,

Bluet‐Pajot³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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Cold resistance appears altered with aging. Among existing hypotheses, the impaired capacity in response to cold could be related to an altered regulation of plasma IGF-1 concentration. The combined effects of age and cold exposure were studied in a short-living primate, the gray mouse lemur (Microcebus murinus), which adjusts its energy balance using a daily torpor phase, to avoid high energy cost of normothermia maintenance. Changes in body mass, core temperature, locomotor activity, and caloric intake were monitored under 9-day exposures to 25 degrees C and 12 degrees C in captive animals in winter conditions. Short-term (after 2 days) and long-term (after 9 days) cold-induced changes in IGF-1 levels were also evaluated. In thermoneutral conditions (25 degrees C), general characteristics of the daily rhythm of core temperature were preserved with age. At 12 degrees C, age-related changes were mainly characterized by a deeper hypothermia and an increased frequency of torpor phases, associated with a loss of body mass. A short-term cold-induced decrease in plasma IGF-1 levels was observed. IGF-1 levels returned to basal values after 9 days of cold exposure. No significant effect of age could be evidenced on IGF-1 response. However, IGF-1 levels of cold-exposed aged animals were negatively correlated with the frequency of daily torpor. Responses exhibited by aged mouse lemurs exposed to cold revealed difficulties in the maintenance of normothermia and energy balance and might involve modulations of IGF-1 levels.

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“…Physiological aging has been defined in recent animal studies by dysfunction in vital organ systems that forecast imminent death more accurately than chronological age (McDonald et al, 1996(McDonald et al, , 1999Tankersley et al, 2003;Frank & Tankersley, 2002). While the assesment of physiological aging may differ among various rodent models, the inability to maintain vital regulatory mechanisms during a period of terminal senescence appears to be a common feature across species.…”

Section: G Tankersley Et Almentioning

confidence: 99%

Particle Effects on Heart-Rate Regulation in Senescent Mice

Tankersley

Campen

Bierman

et al. 2004

Inhalation Toxicology

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Because epidemiology studies consistently identify the elderly at risk for air pollution-related morbidity and mortality, we developed a model of senescent-dependent susceptibility based on indices of physiological aging. In the current study, we hypothesized that heart-rate regulation during particulate matter (PM) exposure differs with senescence-dependent susceptibility owing to variation in autonomic nervous control. Heart rate (HR) and heart-rate variability (HRV) parameters were measured from 162 samples of 2-min electrocardiograph (ECG) recordings in age-matched healthy (n = 5) and terminally senescent (n = 3) AKR mice during 3-h exposures to filtered-air (FA, day 1) and carbon black (CB, day 4; <200 µg/m 3 ). On day 1, HR was significantly (p < .01) depressed during FA in terminally senescent mice. By day 4, HR was further slowed significantly (p < .01) due to the effects of CB exposure for 3 days. The combined effects of terminal senescence and CB exposure acted to depress HR to an average (±SEM) 445 ± 40 bpm, or ∼80 bpm lower compared to healthy HR responses. The change in rMSSD, an HRV parameter corresponding to relative influences of parasympathetic tone on HR, was significantly (p < .01) greater on day 1 and day 4 in terminally senescent mice compared to healthy mice. In contrast, the LF/HF ratio, an HRV parameter derived from spectral analysis indicating relative changes in cardiac sympathetic tone, was significantly (p < .01) depressed in terminally senescent mice on day 1. By day 4, significant increases in LF/HF were evident in healthy mice during CB exposure, suggesting that HR regulation was associated with an increase in sympathetic tone. Alternatively, terminally senescent mice appeared to modulate a lower HR without change in LF/HF ratio during CB exposure, suggesting an absence of sympathetic tone. In conclusion, older healthy mice increase cardiac sympathetic tone during PM exposure while terminally senescent mice show a greater PM-induced parasympathetic tone in regulating HR. The significance of the current results suggest that PM-induced HR regulatory changes may ultimately depend on the degree of physiological aging.

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Alterations in endogenous circadian rhythm of core temperature in senescent Fischer 344 rats

Cited by 19 publications

References 24 publications

Senescent terminal weight loss in the male F344 rat

Senescent terminal weight loss in the male F344 rat

Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus

Particle Effects on Heart-Rate Regulation in Senescent Mice

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