Journal Of Gerontology[JOURNAL]
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200 papers
Brinley plots and theories of aging: the explicit, muddled, and implicit debates.
Fisk AD, Fisher DL
J Gerontol · 1994 Mar · PMID 8126363 · Publisher ↗
We evaluated the debates concerning Brinley plots and the associated theories of age-related slowing. We concluded that an explicit debate regarding a single-factor, general slowing model was no longer a debate as most,...
We evaluated the debates concerning Brinley plots and the associated theories of age-related slowing. We concluded that an explicit debate regarding a single-factor, general slowing model was no longer a debate as most, if not all, agree to the disconfirmation of that model. We address sources of confusion in the debates that have muddled the areas of genuine disagreement. When the confusion is lifted, the remaining debate centers, rightly, on evaluation of theories of aging. We show that Brinley plot analyses can lead to both falsely accepting and falsely rejecting theories of age-related slowing. Although plotting data most certainly can assist with the evaluation of cognitive theory, we argue that models of performance and learning must play a more central role in advancing theories of cognitive aging.
Brinley plots, explained variance, and the analysis of age differences in response latencies.
Myerson J, Wagstaff D, Hale S
J Gerontol · 1994 Mar · PMID 8126362 · Publisher ↗
Critics of Brinley plot analyses (e.g., Fisk, Fisher, & Rogers, 1992; Perfect, 1994) claim: (a) that lack of overlap between latencies on different tasks inflates r2 values; (b) that Brinley plots mask task-specific age...
Critics of Brinley plot analyses (e.g., Fisk, Fisher, & Rogers, 1992; Perfect, 1994) claim: (a) that lack of overlap between latencies on different tasks inflates r2 values; (b) that Brinley plots mask task-specific age differences; and (c) that measurement error in young adults' latencies precludes the use of regression techniques with Brinley plot data. We dispute these claims. We show that lack of overlap does not inflate r2 and that the possible presence of task-specific effects in Brinley plot data may be evaluated using standard regression techniques. These techniques are illustrated using data from the Fisk and Rogers (1991) study of visual and memory search. Analysis of their data reveals significant differences between the lexical and nonlexical domains, but not between types of search. Finally, the effect of measurement error on Brinley plot analyses is shown to be small and, if taken into account, leads to increased support for general cognitive slowing.
Generalized slowing in Brinley plots.
Cerella J
J Gerontol · 1994 Mar · PMID 8126361 · Publisher ↗
The logic of generalized slowing theories is explored. Existing theories are reviewed briefly and put in a common format. The format is readily generalized to define a class of one-dimensional aging theories, a tiny subs...
The logic of generalized slowing theories is explored. Existing theories are reviewed briefly and put in a common format. The format is readily generalized to define a class of one-dimensional aging theories, a tiny subset of all possible aging theories. A corresponding class of compatible data is demonstrated, in terms of allowable configurations of a Brinley plot. Nonconforming configurations have the force of disconfirming the entire class of aging theories. Information processing theories can be cast in a similar format. It is shown that, for a slowing theory to be indisputably general, it must be associated with a multidimensional information processing theory.
What can Brinley plots tell us about cognitive aging?
Perfect TJ
J Gerontol · 1994 Mar · PMID 8126360 · Publisher ↗
The use of Brinley plots (the plotting of the mean response latencies of old adults against the mean latencies for younger adults) has recently become increasingly popular, not least because simple, coherent functions ca...
The use of Brinley plots (the plotting of the mean response latencies of old adults against the mean latencies for younger adults) has recently become increasingly popular, not least because simple, coherent functions can be determined that account for a large proportion of the variance in performance across tasks. This has led some authors to question the need for a modular approach to cognitive aging and has led to attempts to replace such an approach with accounts based on global central nervous system factors. However, use of simulated data to test the efficacy of Brinley plots shows that their apparent success in predicting high levels of variance may be misleading in two ways: (a) Brinley type plots fail to detect occasions when data are generated specifically not to conform to a single function; and (b) the parameter values obtained differ significantly from the underlying functions used to generate the test data. It is suggested that high correlations between young and old reaction times across tasks that have been widely reported in the literature are not in themselves sufficient to support the strong claims made regarding global models of cognitive aging.
Motion perception and Alzheimer's disease.
Gilmore GC, Wenk HE, Naylor LA … +1 more , Koss E
J Gerontol · 1994 Mar · PMID 8126359 · Publisher ↗
The motion sensitivity of 15 probable Alzheimer disease (AD) patients and 15 healthy elderly adults was investigated with a correlated motion paradigm. The AD patients exhibited significantly higher thresholds for detect...
The motion sensitivity of 15 probable Alzheimer disease (AD) patients and 15 healthy elderly adults was investigated with a correlated motion paradigm. The AD patients exhibited significantly higher thresholds for detecting the direction of motion. Contrast sensitivity for a 2 cpd, 7.5 Hz counterphased stimulus was related to motion threshold in the AD group. There also was a significant relationship between an index of dementia severity, Mini-Mental State Exam (MMSE), and motion sensitivity. The results support the hypothesis proposed from neuroanatomical evidence by Hof and Morrison (1990) that AD results in a disruption of the visual signals mediated by area 17. Further, the data suggest that this disruption of visual processing is linked to the progression of dementia. The study offers support for the hypothesis that AD leads to a deficit in the magnocellular or M pathway of visual processing.
Age differences in causal attributions from an adult developmental perspective.
Blanchard-Fields F
J Gerontol · 1994 Mar · PMID 8126358 · Publisher ↗
Causal attributions for events varying on level of informational ambiguity, outcome valence (positive, negative), and situation (relationship, achievement) were examined among young, middle-aged, and older adults. Partic...
Causal attributions for events varying on level of informational ambiguity, outcome valence (positive, negative), and situation (relationship, achievement) were examined among young, middle-aged, and older adults. Participants rated the degree to which a cause of an event was a function of the primary character, situation, or a combination of both (interactive attributions). All adults made interactive attributions for ambiguous events, dispositional attributions with increasing involvement of the primary character, and situational attributions with less involvement of the primary character. Older adults made more interactive attributions in relationship situations and more dispositional attributions in negative situations. For achievement situations, younger adults made more interactive attributions for ambiguous events.
Attention and performance in miniature golf across the life span.
Molander B, Bäckman L
J Gerontol · 1994 Mar · PMID 8126357 · Publisher ↗
Highly skilled adolescent (15-19 years), young (25-35 years), middle-aged (50-57 years), and older (58-73 years) miniature golf players were examined in training and competitive conditions. Number of shots, heart rate, r...
Highly skilled adolescent (15-19 years), young (25-35 years), middle-aged (50-57 years), and older (58-73 years) miniature golf players were examined in training and competitive conditions. Number of shots, heart rate, ratings of anxiety, and concentration time were registered. IN addition, two attentional subscales from the Test of Attentional and Interpersonal Style (TAIS) inventory (Nideffer, 1976) were administered. Results indicated (a) parallel increases of heart rate and rated anxiety in competition for all age groups, (b) improvement of motor performance in competition for adolescent and young-adult players, and deterioration of motor performance in competition for middle-aged and older players, and (c) increased concentration time for the two younger samples, and decreased concentration time for the two older samples in competition. As well, the TAIS data indicated greater self-perceived external and internal distractability in the two older, compared to the two younger samples. This age-related vulnerability to distractions was shown to partly mediate age differences in competitive motor performance. The overall pattern of outcome is discussed relative to the view that the adult aging process is associated with a deficit in the ability to handle situations of high arousal due to age-related deficits in a variety of basic cognitive capacities.
A short physical performance battery assessing lower extremity function: association with self-reported disability and prediction of mortality and nursing home admission.
Guralnik JM, Simonsick EM, Ferrucci L … +5 more , Glynn RJ, Berkman LF, Blazer DG, Scherr PA, Wallace RB
J Gerontol · 1994 Mar · PMID 8126356 · Publisher ↗
BACKGROUND: A short battery of physical performance tests was used to assess lower extremity function in more than 5,000 persons age 71 years and older in three communities. METHODS: Balance, gait, strength, and enduranc...
BACKGROUND: A short battery of physical performance tests was used to assess lower extremity function in more than 5,000 persons age 71 years and older in three communities. METHODS: Balance, gait, strength, and endurance were evaluated by examining ability to stand with the feet together in the side-by-side, semi-tandem, and tandem positions, time to walk 8 feet, and time to rise from a chair and return to the seated position 5 times. RESULTS: A wide distribution of performance was observed for each test. Each test and a summary performance scale, created by summing categorical rankings of performance on each test, were strongly associated with self-report of disability. Both self-report items and performance tests were independent predictors of short-term mortality and nursing home admission in multivariate analyses. However, evidence is presented that the performance tests provide information not available from self-report items. Of particular importance is the finding that in those at the high end of the functional spectrum, who reported almost no disability, the performance test scores distinguished a gradient of risk for mortality and nursing home admission. Additionally, within subgroups with identical self-report profiles, there were systematic differences in physical performance related to age and sex. CONCLUSION: This study provides evidence that performance measures can validly characterize older persons across a broad spectrum of lower extremity function. Performance and self-report measures may complement each other in providing useful information about functional status.
A prospective study of postural balance and risk of falling in an ambulatory and independent elderly population.
Maki BE, Holliday PJ, Topper AK
J Gerontol · 1994 Mar · PMID 8126355 · Publisher ↗
BACKGROUND: An ability to predict risk of future falling is needed in order to target high-risk individuals for preventive intervention. The purpose of this study was to compare the ability of different measures of postu...
BACKGROUND: An ability to predict risk of future falling is needed in order to target high-risk individuals for preventive intervention. The purpose of this study was to compare the ability of different measures of postural balance to predict risk of falling prospectively in an ambulatory and independent elderly population. METHODS: Balance tests were performed on 100 volunteers (aged 62-96), and falling was then monitored prospectively over a one-year period. The balance testing comprised measurements of: (a) spontaneous postural sway, (b) induced anterior-posterior sway, (c) induced medial-lateral sway, (d) anticipatory adjustments preceding volitional arm movements, (e) timed one-leg stance, and (f) performance on a clinical balance assessment scale. Small pseudorandom platform motions were used to perturb balance in the induced-sway tests. Using force plates, the spontaneous- and induced-sway responses were quantified in terms of the amplitude, speed, and mean frequency of the center-of-pressure displacement; input-output models were also used to parameterize the induced-sway performance. RESULTS: Although a number of measures showed evidence of significant differences between fallers and nonfallers, the differences were most pronounced for measures related to the control of lateral stability. Lateral spontaneous-sway amplitude (blindfolded conditions) was found to be the single best predictor of future falling risk, particularly for the large group of falls that were precipitated by a biomechanical perturbation. This measure was able to predict future falling risk with moderate accuracy, even in those individuals with no recent history of falling. CONCLUSIONS: The results suggest that control of lateral stability may be an important area for fall-preventative intervention. The ability of a simple and safe force-plate measure of spontaneous postural sway to predict future falling risk suggests a possible clinical application as a preliminary screening tool for risk of falling.
Multisensory training of standing balance in older adults: II. Kinematic and electromyographic postural responses.
Hu MH, Woollacott MH
J Gerontol · 1994 Mar · PMID 8126354 · Publisher ↗
BACKGROUND: The purpose of this study was to analyze the electromyographic and kinematic characteristics of postural responses of 24 healthy older adults both prior to and immediately after a multisensory balance trainin...
BACKGROUND: The purpose of this study was to analyze the electromyographic and kinematic characteristics of postural responses of 24 healthy older adults both prior to and immediately after a multisensory balance training period. It was hypothesized that the muscle and movement characteristics of postural responses would be optimized in the group after training. METHODS: Balance was tested by determining muscle and kinematic response characteristics used in compensating for support surface displacements. Twenty-four subjects were randomly assigned to a training group or a control group. The training group received a multisensory balance training program during a 15-day training period (described in the companion article). RESULTS: The results showed that the training (a) significantly shortened the onset latency of the neck flexor muscle (p < .05); (b) showed a trend toward decreasing the response frequency of antagonist muscles; (c) showed a trend toward increasing the response frequency of the trunk flexor muscles; and (d) showed a trend toward decreasing the maximal excursion of the first-trial of the ankle joint rotation. CONCLUSIONS: From these results and those of the companion article, it was concluded that the multisensory balance training program had an effect in optimizing the muscle and movement characteristics of postural response in the training group older adults.
Multisensory training of standing balance in older adults: I. Postural stability and one-leg stance balance.
Hu MH, Woollacott MH
J Gerontol · 1994 Mar · PMID 8126353 · Publisher ↗
BACKGROUND: The effects of standing balance training on the ability to maintain stability in both static two-leg and one-leg stance were tested in healthy older adults. METHODS: Subjects (age range 65-90 years) were rand...
BACKGROUND: The effects of standing balance training on the ability to maintain stability in both static two-leg and one-leg stance were tested in healthy older adults. METHODS: Subjects (age range 65-90 years) were randomly assigned to a training (n = 12) or control group (n = 12). Training subjects received a 10-hour balance training program which selectively manipulated sensory inputs from the visual, vestibular, and somatosensory systems. RESULTS: Training subjects showed significantly improved stability (root-mean-square values of anteroposterior platform torque) after training in five of the eight training conditions (when somatosensory inputs were changed or when two or more sensory systems were simultaneously manipulated) (p < .006). When tested 4 weeks after completion of training, subjects (a) fell less frequently when the ankle/foot somatosensory inputs were minimized and (b) stood longer on one leg than the control group (p < .001). CONCLUSIONS: Balance training designed to improve intersensory interaction could effectively improve balance performance in healthy older adults.
Do activities of daily living have a hierarchical structure? An analysis using the longitudinal study of aging.
Lazaridis EN, Rudberg MA, Furner SE … +1 more , Cassel CK
J Gerontol · 1994 Mar · PMID 8126352 · Publisher ↗
BACKGROUND: It has long been thought that individual activities of daily living (ADLs) can be combined to form a hierarchy or Guttman scale. The purpose of this study is to determine if ADLs fit into a single hierarchica...
BACKGROUND: It has long been thought that individual activities of daily living (ADLs) can be combined to form a hierarchy or Guttman scale. The purpose of this study is to determine if ADLs fit into a single hierarchical structure, and to examine how such a hierarchy should be evaluated. METHODS: We use data from the baseline year of the Longitudinal Study of Aging, a nationally representative survey of noninstitutionalized persons 70 years of age and older. For each of the 360 permutations of the ADLs within the Katz hierarchy, we calculate the standard measures of fit of ordered data to a Guttman scale: the coefficient of reproducibility, the minimum marginal reproducibility, the percentage improvement, and the coefficient scalability. RESULTS: We find that although the Katz hierarchy does satisfy the traditional requirements for scalability, many other ADL hierarchies also satisfy these criteria. Specifically, our analysis shows that there are 4 hierarchies at least as good as the Katz hierarchy, and 103 hierarchies which satisfy the minimum standard for scalability. CONCLUSIONS: We conclude that the typical scalogram methodology may not be sufficient to summarize data, and that a multiplicity of disability profiles may exist.
L-arginine reduces kidney collagen accumulation and N-epsilon-(carboxymethyl)lysine in the aging NMRI-mouse.
Radner W, Höger H, Lubec B … +2 more , Salzer H, Lubec G
J Gerontol · 1994 Mar · PMID 8126351 · Publisher ↗
BACKGROUND: The aging process leads to glomerular basement membrane (GBM) thickening due to increased collagen accumulation. This mechanism can be explained by the nonenzymatic glycosylation hypothesis of collagen aging....
BACKGROUND: The aging process leads to glomerular basement membrane (GBM) thickening due to increased collagen accumulation. This mechanism can be explained by the nonenzymatic glycosylation hypothesis of collagen aging. We have published the positive effect of L-arginine on glucose-mediated cross-linking, and if the nonenzymatic glycosylation hypothesis of aging holds, the pharmacological effect of L-arginine on glucose-mediated cross-links in the aging Hannover NMRI mouse can be expected. METHODS: Animals were given L-arginine 50 mg/kg body weight/day orally and compared to a control group without treatment. RESULTS: Electron microscopical measurement of the GBM thickness showed significant differences between controls (4920 +/- 1680 A) and the experimental group (2345 +/- 815 A). Determination of the total kidney collagen content based upon 4-trans hydroxyproline revealed 13.9 +/- 3.9 mg/100 mg kidney weight (kw) in the untreated group versus 7.9 +/- 4.2 mg/100 mg kw in the treated group. For solubility studies based upon hydroxyproline determination, collagen was eluted by pepsin digestion. This revealed 18.7 +/- 3.9 mg/100 mg kw in the controls versus 7.8 +/- 4.8 mg/100 mg kw in the treated group. HPLC analysis of N-epsilon-(carboxymethyl)lysine (CML) showed in the treated group (1.847 +/- 0.247 nM/microM hydroxyproline) significantly lower concentrations than in the untreated group (3.399 +/- 0.349 nM/microM hydroxyproline). On sodium dodecyl sulfate (SDS) polyacrylamidegel electrophoresis, the eluates of the treated animals showed less high molecular weight material than their untreated mates. CONCLUSIONS: We cannot discriminate between the probable mechanisms of cross-linking but we clearly can state that L-arginine reduces cross-linking and collagen accumulation in aging collagen type IV accompanied and strongly associated with decreased CML content.
Split-virus influenza vaccines: do they provide adequate immunity in the elderly?
McElhaney JE, Meneilly GS, Lechelt KE … +1 more , Bleackley RC
J Gerontol · 1994 Mar · PMID 8126350 · Publisher ↗
BACKGROUND: Senescence of T-cell function increases susceptibility to influenza with aging. In healthy elderly, we have found that inactivated whole-virus vaccine (WVV) effectively boosts helper T-cell (Th)-mediated immu...
BACKGROUND: Senescence of T-cell function increases susceptibility to influenza with aging. In healthy elderly, we have found that inactivated whole-virus vaccine (WVV) effectively boosts helper T-cell (Th)-mediated immunity. Recently, however, the use of WVV has been superseded by split-virus vaccine (SVV) to questionably reduce adverse effects of vaccination. METHODS: Healthy young adults were compared to healthy elderly adults for their response to SVV. Peripheral blood mononuclear cells (PBMC) obtained pre-vaccination and 6 and 12 weeks post-vaccination, were cultured with live influenza virus, and supernatant IL2 activity was measured. RESULTS: Both groups showed an increase in in vitro IL2 activity by 6 weeks post-vaccination but IL2 decreased to pre-vaccination levels by 12 weeks. Young and elderly adults who had received WVV one year prior did not respond to SVV in this study. CONCLUSIONS: SVV does not provide Th-mediated immunity for the duration of the flu season and may actually suppress Th-mediated immunity in previous recipients of WVV.
Influence of age and long-term dietary restriction on enzymatically mediated crosslinks and nonenzymatic glycation of collagen in mice.
Reiser KM
J Gerontol · 1994 Mar · PMID 8126349 · Publisher ↗
This study was designed to investigate the effects of lifetime diet restriction on collagen crosslinking in skin, tail tendon, aorta, and lung in mice. Difunctional enzymatic crosslinks decreased with age in all tissues...
This study was designed to investigate the effects of lifetime diet restriction on collagen crosslinking in skin, tail tendon, aorta, and lung in mice. Difunctional enzymatic crosslinks decreased with age in all tissues except skin, while mature crosslinks showed almost no change with age. Collagen-associated fluorescence, assayed in skin and tail tendon, increased with age, as did pentosidine, a specific advanced glycation product, in aorta. There was no change in glucitolyllysine content with age. Difunctional crosslinks, glucitolyllysine, and collagen-associated fluorescence were decreased in diet-restricted animals relative to ad libitum fed animals in some tissues at some time points; however, correlations were not observed among these different effects, or between different tissues. Diet restriction did not affect nonreducible "mature" crosslinks. These studies suggest that: (1) lifetime diet restriction is associated with decreased collagen-associated fluorescence, suggestive of advanced glycation products, in older animals; (2) age-related increases in collagen stiffening and its decrease by dietary restriction cannot be explained solely by alterations in lysyl oxidase-mediated crosslinking, the levels of which are tissue dependent; (3) lysyl oxidase-mediated crosslinking and nonenzymatic glycation of collagen are independently influenced by dietary restriction and aging.
Stress response of senescent T lymphocytes: reduced hsp70 is independent of the proliferative block.
Effros RB, Zhu X, Walford RL
J Gerontol · 1994 Mar · PMID 8126348 · Publisher ↗
Senescent human T lymphocyte cultures are unable to undergo proliferation, but show no difference from early passage cells in cytotoxic function or surface antigenic profile. A second feature of senescent T cells is the...
Senescent human T lymphocyte cultures are unable to undergo proliferation, but show no difference from early passage cells in cytotoxic function or surface antigenic profile. A second feature of senescent T cells is the dramatic reduction in hsp70 production in response to heat shock. This decline is associated with a decrease in binding of nuclear extracts to the consensus heat shock element. Interestingly, the progressive decline in the heat shock response of cultured T cells correlates with the percent proliferative life span completed rather than with the actual proliferative activity at the time of heat shock. This suggests that for senescent T cells the reduced ability to respond to heat shock by producing hsp70, although possibly lying at the level of transcriptional control, may nevertheless be unrelated to the reduced DNA synthesis or the diminished proliferative activity also manifested by these cells.
Discordance between thermogenic activity and expression of uncoupling protein in brown adipose tissue of old rats.
Yamashita H, Yamamoto M, Ookawara T … +3 more , Sato Y, Ueno N, Ohno H
J Gerontol · 1994 Mar · PMID 8126347 · Publisher ↗
To elucidate the reason why thermogenic ability is impaired with age, the relationship between thermogenic activity and gene expression of several proteins including uncoupling protein (UCP) in brown adipose tissue (BAT)...
To elucidate the reason why thermogenic ability is impaired with age, the relationship between thermogenic activity and gene expression of several proteins including uncoupling protein (UCP) in brown adipose tissue (BAT) was investigated in 24-month-old rats. Compared to young (3-month-old) rats, a significant decrease in BAT/body mass ratio and considerable changes of chemical components in BAT were observed in the old rats. This indicates a marked decrease in the thermogenic capacity in BAT of the old rats. Likewise, the thermogenic activity (which was assessed by guanosine 5'-diphosphate binding to BAT mitochondria) was greatly reduced in the mitochondria recovered from BAT of the old rats. However, the UCP content in the BAT mitochondria was similar in both groups. Conversely, the expression of UCP mRNA was greater in the old rats than in the young rats. These results suggest that the regulation on and after UCP translation may be concerned with impaired BAT thermogenic activity due to aging. Moreover, the mRNA levels of several other proteins including insulin-sensitive glucose transporter concerned in BAT thermogenesis changed with age, suggesting that the mRNA levels may be affected in order to compensate for the decline in the thermogenic activity in the old rats.
The interaction of ethanol with the cognitive enhancers tacrine, physostigmine, and AIT-082.
Ritzmann RF, Glasky A, Steinberg A … +1 more , Melchior CL
J Gerontol · 1994 Mar · PMID 8126346 · Publisher ↗
Because tacrine, a cognitive enhancing agent, was being considered for approval for use in Alzheimer's disease, its possible interaction with ethanol, a commonly used substance to which elderly individuals are generally...
Because tacrine, a cognitive enhancing agent, was being considered for approval for use in Alzheimer's disease, its possible interaction with ethanol, a commonly used substance to which elderly individuals are generally more sensitive than younger individuals, was explored. For purposes of comparison, two other drugs, which have also been shown to improve memory in mice, at doses which had activity in a working memory paradigm, were evaluated for an interaction with ethanol. Ethanol-induced sedation in mice was increased by tacrine and decreased by physostigmine, whereas AIT-082 did not alter sedation. However, tacrine had no effect on body temperature or on ethanol-induced hypothermia. Neither tacrine nor physostigmine had any effect on the rate of ethanol elimination from the blood. As tacrine comes into clinical use in the treatment of Alzheimer's disease, adverse interactions with ethanol should be explored further.
The Brown Norway rat as a model of male reproductive aging: evidence for both primary and secondary testicular failure.
Gruenewald DA, Naai MA, Hess DL … +1 more , Matsumoto AM
J Gerontol · 1994 Mar · PMID 8126345 · Publisher ↗
In man, aging is associated with both primary and secondary testicular dysfunction. In contrast, most studies in male rat models of aging have demonstrated only secondary testicular failure. We previously reported that t...
In man, aging is associated with both primary and secondary testicular dysfunction. In contrast, most studies in male rat models of aging have demonstrated only secondary testicular failure. We previously reported that testes from aging male F344 rats secrete excessive progesterone (P), which may suppress gonadotropin secretion and confound aging studies. To determine whether the male Brown Norway (BN) rat is a more suitable aging model, trunk blood was collected from intact (sham-operated) and orchidectomized young (3 mo), middle-aged (13 mo), old (23 mo), and senescent (28-30 mo) animals. Testosterone (T), estradiol (E2), P, prolactin (PRL), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured by RIA. In intact rats, T levels declined with aging, while LH was unchanged, and FSH increased progressively with aging. In contrast to F344 rats, no age-related increases in P or E2 occurred, nor did PRL or other steroid hormones increase. In the absence of testicular feedback (orchidectomized rats), FSH and LH declined progressively with aging. These findings suggest that, as in men, aging male BN rats manifest both primary and secondary testicular failure, and do not exhibit decreased gonadotropin levels secondary to excessive steroid or PRL secretion. Therefore, the BN rat appears to be the best available rat model for studies of male reproductive aging.
Role of adrenocortical steroids in mediating cancer-preventive and age-retarding effects of food restriction in laboratory rodents.
Schwartz AG, Pashko LL
J Gerontol · 1994 Mar · PMID 8126344 · Publisher ↗
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