Showing papers in "Journal of Gerontology in 1979"
TL;DR: Self-reports of health were found to be significantly correlated with ratings assigned by a physician on the basis of medical records, and both types of measures were predictive of differences in survival time among the younger subjects in the sample, but neither was significantly related to longevity for older subjects.
Abstract: The present study was designed to provide information on the relationship between self-reports of health and physicians' ratings in an aged sample, and to determine how both of these measures of health relate to longevity. Subjects were 69 survivors (median age = 84.25 years) of a sample of aged twins who had been followed longitudinally since 1947 to 1949. Self-reports of health were found to be significantly correlated with ratings assigned by a physician on the basis of medical records. Both types of measures were predictive of differences in survival time among the younger subjects in the sample, but neither was significantly related to longevity for older subjects. The results suggest that self-reports could provide a valid, cost-effective means of health assessment in studies in which other forms of health information are lacking.
394 citations
TL;DR: Treatment with FUdR under carefully controlled conditions is a reasonable way to maintain synchronously aging populations of C. elegans, and age-associated changes seen in controls also occurred in F UdR-treated worms, including atrophy of the gonads, increased pigmentation, sluggishness and increased transparency.
Abstract: Fluorodeoxyuridine (FUdR), an inhibitor of DNA synthesis, was examined for its ability to prevent a synchronous population of C. elegans from reproducing without otherwise interfering with the organism's post-maturational development and aging. When a synchronized population was exposed to 400 micrometer FUdR just as the population reached sexual maturity, the FUdR induced complete sterility within five hours by preventing eggs from hatching. Any larvae that hatched from eggs made before the FUdR was added remained small in the presence of FUdR and were easily removed by filtration or sedimentation. FUdR-sterilized adults showed no morphological abnormalities. Age-associated changes seen in controls also occurred in FUdR-treated worms, including atrophy of the gonads, increased pigmentation, sluggishness and increased transparency. Life span was not shortened by FUdR treatment. Our observations suggest that treatment with FUdR under carefully controlled conditions is a reasonable way to maintain synchronously aging populations of C. elegans.
229 citations
TL;DR: A path analysis model of life satisfaction is proposed and applied to data from interviews with 141 persons aged 60 years and over, finding health and activity emerge as strong predictors ofLife satisfaction while income influences life satisfaction indirectly via activity.
Abstract: A path analysis model of life satisfaction is proposed and applied to data from interviews with 141 persons aged 60 years and over. Predictor variables examined are self-reported health, income, education and an activity index. The analysis was conducted separately for the two sexes. Health and activityemerge as strong predictors of life satisfaction while income influences life satisfaction indirectly via activity. The importance of investigating direct and indirect effects of variables via path analysis is discussed.
225 citations
TL;DR: Age-related differences in the ability to learn new color and pattern discrimination problems of varying difficulty suggest that aging impairs mechanisms involved with response rigidity and/or susceptibility to intertrial proactive interference, more severely than those involved with the simple formation of new associations.
Abstract: The behavior of aged rhesus monkeys (18 years and older) was compared to that of young monkeys (3 to 6 years old) to evaluate their relative abilities to learn a series of visual discrimination and discrimination reversal problems. Using a subject-paced, automated experimental procedure designed to optimize stimulus control and facilitate execution of choice responses, no consistent age-related differences were observed in the ability to learn new color and pattern discrimination problems of varying difficulty. However, a severe and consistent deficity on reversal learning did occur. A detailed analysis of this deficit revealed that not only did the aged monkeys take longer to extinguish the old habit and return to chance performance, but they continued to display a deficit in establishing accurate performance at above-chance levels as well. Since no reliable age differences were observed on the original discrimination learning problems, these data suggest that aging impairs mechanisms involved with response rigidity and/or susceptibility to intertrial proactive interference, more severely than those involved with the simple formation of new associations.
179 citations
TL;DR: It is suggested that the quality, rather than quantity, of social interaction is crucial to understanding adaptations to old age.
Abstract: Problems of social and psychological adjustment in later life have been examined by numerous investigators. Some have found positive relationships between social interaction and personal adjustment, while others have found interaction and adjustment to be unrelated. The purpose of the research reported here was to examine how different ways of measuring interaction may affect its relationship with personal adjustment. Data were obtained in interviews with 218 noninstitutionalized persons aged 70 and older. Findings indicate that both the number of persons interacted with, and the frequency of this interaction, are of little importance for the adjustment of older people. We suggest that the quality, rather than quantity, of social interaction is crucial to understanding adaptations to old age.
154 citations
TL;DR: The increase in the number of multinucleated cells found during the period of observation showed that progressive changes occur in Phase III and no sign of spontaneous acquisition of infinite proliferative potential was observed.
Abstract: Senescent human diploid cell cultures (WI-38 and WI-26) were studied during Phase III for survival time, ability to synthesize DNA, and nuclear morphology. Periodic transfers made during a 6-month period of Phase III showed that cultures were maintained with only slight variations in cell number. No sign of spontaneous acquisition of infinite proliferative potential was observed. The increase in the number of multinucleated cells found during the period of observation showed that progressive changes occur in Phase III. A certain proportion of cells maintained the ability to incorporate tritiated thymidine throughout the period of observation.
150 citations
TL;DR: Although an age-related decrease in salt taste acuity was observed, the decrement was smaller than previously reported in other studies and probably exaggerated taste deficits in the elderly.
Abstract: Salt taste detection thresholds were measured in 76 adults aged 23 to 92 years using a forced-choice staircase procedure, with distilled water rinses between all stimuli. Although an age-related decrease in salt taste acuity was observed, the decrement was smaller than previously reported in other studies. Past reports have probably exaggerated taste deficits in the elderly, because adequate rinse procedures and controls for subject response biases have not been incorporated in threshold measures.
123 citations
TL;DR: Little intellectual decline was seen in these superior subjects until very late in life, and analyses based on such superior subjects without reference to the larger body of subject populations can lead to spurious generalizations about aging in general.
Abstract: Two hundred and forty-six subjects aged 60 to 94 were tested with the WAIS at test session 1, the start of a longitudinal study which lasted approximately 20 years. The subject attrition from the first session to the last (session No. 11) was progressive and selective, leaving mainly the intellectually superior ones in the study. Two facts appeared particularly important: One, little intellectual decline was seen in these superior subjects until very late in life. Two, analyses based on such superior subjects without reference to the larger body of subject populations can lead to spurious generalizations about aging in general. Age decline in intellectual ability seen in more representative populations may not be apparent when analyzing data of select samples.
106 citations
TL;DR: Younger age perceptions were associated with better psychological functioning in Blacks and whites as well as in males and females, even when social class, disability, and impairment were controlled.
Abstract: One hundred-fifty persons age 65 and over who identified themselves as feeling younger, or as old or older than their age, were studied in terms of seven dependent variables describing psychological functioning. Younger age perceptions were associated with better psychological functioning in Blacks and whites as well as in males and females. This was true even when social class, disability, and impairment were controlled. The variable which discriminated best between perceived age groups was locus of control, with more internality being associated with younger age perceptions.
103 citations
TL;DR: The results indicate that the density of astrocytes exhibiting hypertrophy in the hippocampus increases dramatically and progressively with age, being significantly elevated even in mid-life (13 month) animals, and of particular note was the finding thatAstrocyteHypertrophy is far more prominent in synaptic terminal fields than in myelinated fibers of the same system.
Abstract: Our results indicate that the density of astrocytes exhibiting hypertrophy in the hippocampus increases dramatically and progressively with age, being significantly elevated even in mid-life (13 month) animals. However, the total population of astrocytic cells (hypertrophied and nonhypertrophied) in the quantified region is not significantly elevated. Further, the relative distributions of both hypertrophied and total glial cells remained remarkably constant at the three ages measured. Reactive hypertrophy of astrocytes therefore appears to occur "in place" and migration of astrocytes does not appear to be a major factor in the hippocampus during aging. Of particular note was the finding that astrocyte hypertrophy is far more prominent in synaptic terminal fields than in myelinated fibers of the same system.
102 citations
TL;DR: While younger subjects profited more from retrieval cues that were associations they had themselves generated than from retrieval cue types that were normed common associations, older subjects made comparable use of these two cue types.
Abstract: Adults in their twenties and sixties were tested for free recall, cued recall, and recognition of words that they had studied in an intentional memory task or generated associations to in an incidental orienting task. Significant age-related declines in performances on intentional items were observed regardless of type of memory test. Significant age-related declines in performance on incidental items were also observed on free and cued recall tests; however, age differences on incidental items were attenuated on cued recall tests, and they were eliminated on recognition tests. In addition, while younger subjects profited more from retrieval cues that were associations they had themselves generated than from retrieval cues that were normed common associations, older subjects made comparable use of these two cue types.
TL;DR: There appeared to be little, if any, age-related deficit in depth of processing as defined on a sensory-semantic dimension, and age-level differences in retention of old item information were viewed as reflecting differences in the extent of elaboration within a processing domain.
Abstract: Adult age differences in the depth of processing in recognition memory were examined for the three groups with mean ages of 19, 45, and 70 years. Subjects were tested for phonological and semantic false recognitions with a continuous recognition memory procedure using both moderate (4 sec) and slow (8 sec) presentation rates. Both middle-aged and elderly subjects displayed a greater false recognition effect for both rhymes (phonological) and synonyms (semantic) of previously presented items than did young adults. Thus, there appeared to be little, if any, age-related deficit in depth of processing as defined on a sensory-semantic dimension. On the other hand, middle-aged and elderly subjects correctly recognized fewer of the previously presented (i.e., old) items than did the young adults. Age-level differences in retention of old item information were viewed as reflecting differences in the extent of elaboration within a processing domain. Rate of presentation did not affect either processing depth as measured by false recognitions, or memory per se as measured by the recognition of old items.
TL;DR: The results of this study argue against the wide-spread assumption of a decreased blood supply in the cerebral cortex during old age, and show that the capillary net is able to respond to changed metabolism and blood pressure.
Abstract: Capillaries in the cerebral cortex of six age groups, ranging between 19 and 94 years (= 34 human brains) were stereologically investigated. Capillary parameters such as diameter, volume fraction, specific surface area, mean intercapillary distances and total length per unit cortex volume in patients older than 75 years were similar to those in young ones, 19 to 44 years old. Aged subjects between 64 and 74 years revealed increased capillary diameter, volume and total length per unit cortex volume, as well as decreased specific surface area. Frequency distributions in the same age indicate a real increase of capillary diameter and volume, as also an increase of these parameters on the level of blood vessels with diamteres greater than 8 micrometer, probably arterioles. The results of this study argue against the wide-spread assumption of a decreased blood supply in the cerebral cortex during old age. On the contrary, the capillary net is able to respond to changed metabolism and blood pressure.
TL;DR: The weights and individual subject spaces suggested that the ability of subjects to judge qualitative odor differences between food flavors may decrease with age.
Abstract: Sixteen young students, aged 19-25, and 16 healthy elderly subjects, aged 72-78, rated the odor similarity for all 91 combinations of pairs of 14 commercial food flavors. Hedonic ratings were also obtained. Two multidimensional scaling procedures, INDSCAL (Carroll & Chang, 1970) and SSAI-MINISSA (Guttman, 1968; Lingoes, 1965), were applied to the similarity data, yielding flavor spaces or maps which were similar to one another. INDSCAL, an individual difference model, provided weights for each subject on each of the dimensions of a multidimensional space common to all subjects; the weights indicated that the young subjects, but not the elderly ones, were well represented by the common multidimensional arrangement with some idiosyncratic stretching along the axes. The weights and individual subject spaces suggested that the ability of subjects to judge qualitative odor differences between food flavors may decrease with age. Elderly subjects were best at discriminating fruits from the rest of the stimuli.
TL;DR: Five young rats, age 152--175 days, and six old rats, all of the F-344 strain, were compared by electronic methods for amplitude of slow wave activity during sleep and for other sleep parameters.
Abstract: Five young rats, age 152--175 days, and six old rats, age 782--801 days, all of the F-344 strain, were compared by electronic methods for amplitude of slow wave activity during sleep and for other sleep parameters. Unlike humans, who show a pronounced loss of slow wave activity with advanced age, no significant difference in delta activity could be detected between young and old rats. Several hypotheses about the species difference were reviewed. Young and old rats, however, did show several differences in other sleep parameters which parallel those observed in humans. These age-related changes were a moderate decrease in the percent of total sleep time spent in paradoxical sleep, a decrease in the length of sleep bouts, an increase in the number of sleep bouts, and a decrease in the amplitude of the diurnal rhythm of sleep.
TL;DR: The data suggest that the selective age-related loss of synapses involving dendritic spines (but not shafts) in the cerebellar cortex results from the impairment with advanced age of specific afferent neurons and/or a selectiveAge-related vulnerability of dendrite spines.
Abstract: Numbers of synapses were compared in the cerebellar cortex of adult (12 months of age) and senescent (25 months of age) male rats of the Fisher-344 strain. The total number of axodendritic synapses was found to be 24% lower in the senescent rats as compared with adults. A differential analysis of synapses involving dendritic shafts and spines showed no significant change in numbers of synapses involving shafts, but a highly sigificant 33% decrease in numbers involving spines in senescent rats. These data suggest that the selective age-related loss of synapses involving dendritic spines (but not shafts) in the cerebellar cortex results from the impairment with advanced age of specific afferent neurons and/or a selective age-related vulnerability of dendritic spines.
TL;DR: The findings do not support the hypothesis that aging of the central nervous system is related to breakdown of the blood-brain barrier and instead reflect a reduced extracellular space in the older animals.
Abstract: Cerebrovascular permeability to 14C-sucrose was measured in 3-mo-old and 28-mo-old conscious, restrained Fischer 344 male rats. Tracer was injected intravenously in these animals and arterial plasma concentrations were followed for 50 to 240 min, when animals were killed and regional brain radioactivity was measured. Equations derived by a two-compartment diffusion model were fit to concentration data to estimate PA (product of cerebral capillary permeability and surface area) and Ve (cerebral distribution space of 14C-sucrose). PA in 3-mo-old rats averaged 7.53 x 10(-6) sec-1 in 14 cerebral regions, and was not significantly elevated in 28-mo-old rats except possibly at white matter. Ve fell from an average of 0.126 in control rats to 0.070 in 28-mo-old rats. This 45% reduction may reflect a reduced extracellular space in the older animals. The findings do not support the hypothesis that aging of the central nervous system is related to breakdown of the blood-brain barrier.
TL;DR: A determination of patch size by bromouracil photolysis following ultraviolet irradiation revealed that the patch sizes were the same for the two species, and that the number of repaired sites was 2.2 times greater for Peromyscus than for Mus, in agreement with the ratio found by measurement of unscheduled DNAmore synthesis.
Abstract: Previous studies have reported a direct correlation between the rate of uv-induced unscheduled DNA synthesis and the maximum lifespan for seven mammalian species drawn from five different orders. We now examine this correlation in laboratory populations of two rodent species, the house mouse, Mus musculus, and the white-footed mouse, Peromyscus leucopus, both in the superfamily Muroidea. These species are similar in body size but Peromyscus exceeds Mus in lifespan by a factor of 2.5, as determined by live table studies in the same laboratory environment. The extent of uv-induced unscheduled DNA synthesis by third-passage primary fibroblast cell cultures was measured for these two species, and the rate of DNA synthesis was 2.5 times greater for the Peromyscus cells, consistent with the greater lifespan of Peromyscus and with the relationship of repair of uv damage to lifespan found previously among representatives of five orders of mammals. A determination of patch size (size of the repair regions) by bromouracil photolysis following ultraviolet irradiation revealed that the patch sizes were the same for the two species, and that the number of repaired sites was 2.2 times greater for Peromyscus than for Mus, in agreement with the ratio found by measurement of unscheduled DNAmore » synthesis. The number of single strand breaks induced by gamma rays, and the rate of rejoining of these breaks, as measured on alkaline sucrose gradients, were not significantly different in the two species.« less
TL;DR: Electron microscopic studies revealed attenuation of capillary walls and declining numbers of endothelial mitochondria per capillary profile with increasing age, which corroborate morphological and biochemical studies indicative of decline numbers of mitochondria, and decreasing mitochondrial ATP synthesis and ATPase activity in other tissues during aging.
Abstract: Samples were obtained from the frontal and occipital cortex of Macaque monkeys at 4, 10 and 20 years of age. Electron microscopic studies revealed attenuation of capillary walls and declining numbers of endothelial mitochondria per capillary profile with increasing age. The basal lamina surrounding the capillary increased in thickness between 4 and 10 years of age; however, it did not undergo further change between 10 and 20 years. These results corroborate morphological and biochemical studies indicative of declining numbers of mitochondria, and decreasing mitochondrial ATP synthesis and ATPase activity in other tissues during aging.
TL;DR: It appears that most of these potential stressors have less serious long-term outcomes than the crisis orientation would suggest.
Abstract: The effects of five major life events, and of three types of resources, on the physical and social-psychological adaptation of 375 participants in a longitudinal study were examined. As expected, medical events had the most impact on physical adaptation, but they had surprisingly little impact on social-psychological adaptation. Retirement had the most negative social-psychological effects, but had little effect on physical adaptation. The other three events had even less effects, although multiple events tended to cumulate in impact. Better physical resources helped only physical adaptation, and better psychological and social resources mainly helped satisfaction. It appears that most of these potential stressors have less serious long-term outcomes than the crisis orientation would suggest.
TL;DR: Results were interpreted as providing no support for the widely belief that the aged are more depressed than any other age group, and it was argued that somatic complaints can be valid indicators of depression in the elderly.
Abstract: Beck Depression Inventory scores were obtained from 48 elderly who had been residing in homes for the aged for more than one year, 31 elderly residing in the community and waiting to enter an old-age home, and 424 young adults enrolled in a fist-year psychology course. The residents of old-age homes reported no more symptoms of depression than the waiting-list controls, a finding that provides no support for the hypothesis that the institional nature of old-age homes increases depression in the elderly. Both the institutionalized and noninstitutionalized aged reported more somatic symptoms of depression than the young adults, but no greater cognitive or affective symptoms of depression. These results were interpreted as providing no support for the widely belief that the aged are more depressed than any other age group. Finally, it was argued that somatic complaints can be valid indicators of depression in the elderly if normative differences between young and old are taken into account.
TL;DR: For both groups, an early component of the ERP was larger to tones in the attended ear than in the unattended ear, and a later component was largest to the target, which suggests that both groups can attenuate irrelevant stimuli and can use stimulus probability information in this task.
Abstract: We used an event-related brain potential (ERP) technique developed by Hillyard et al. (1973) to test abilities to attenuate irrelevant stimuli and to detect target stimuli. Subjects, 12 healthy old (80.3 years) and 12 healthy young adults (22.0 years), heard 1500 Hz tones in one ear and 800 Hz tones in the other ear. Infrequently, the pitch of either tone was raised. During one run, infrequent tones in the right ear were targets, and in the other run those in the left ear were targets. Subjects counted targets. For both groups, an early component of the ERP (N1) was larger to tones in the attended ear than in the unattended ear, and a later component (P3) was largest to the target. This suggests that both groups can attenuate irrelevant stimuli and can use stimulus probability information in this task. That P3 was later for old subjects suggests that they take longer to decide stimulus relevance.
TL;DR: The results suggest that age differences in effects of perceptual noise and response competition are not general phenomena, but depend upon the demand characteristics of the specific task.
Abstract: Elderly (60 to 82 years) and young (18 to 25 years) subjects were tested on a visual task in which noise items were present but did not require processing to test the hypotheses that elderly persons have more difficulty ignoring irrelevent stimuli and suppressing response competition than do younger persons. Tachistoscopically presented displays contained a precued central target letter either alone or flanked by noise items that required (1) a response the same as, or (2) opposite to that required by the target letter, or (3) did not require a response in this task. No evidence was found to support differentially greater response slowing by the elderly due to the presence of irrelevant stimuli. Elderly persons showed significantly less effects of response competition, suggesting that the two groups processed the task information differently. The results suggest that age differences in effects of perceptual noise and response competition are not general phenomena, but depend upon the demand characteristics of the specific task.
TL;DR: The results support the view that lipofuscin represents an integral aspect of aging and may be used as a cellular marker for physiological age whereas lysosomal enzyme activities do not seem to be directly related to the rate of aging.
Abstract: The effect of experimental prolongation of life span on the rate of lipofuscin accumulation in the giant neurons of the brain and lysosomal enzyme activity in the head was studied in the male housefly, Musca domestica. The median and the maximum life span of the flies was extended twofold by varying their flight activity. The rate of lipofuscin accumulation was significantly faster in short-lived, high-activity flies as compared to the long-lived, low-activity flies. The maximal content of lipofuscin in the neurons was similar in both groups but was reached at a much older age in the low-activity flies. Age-associated profiles of the activities of the lysosomal enzymes beta-glycerophosphatase and beta-acetylglucosaminidase did not correspond to the mortality characteristics of the housefly populations. The results support the view that lipofuscin represents an integral aspect of aging and may be used as a cellular marker for physiological age whereas lysosomal enzyme activities do not seem to be directly related to the rate of aging.
TL;DR: Age and the number of variable irrelevant dimensions were the best predictors of reaction time and error scores and there was a disproportionate increase in both reaction times and errors as levels of irrelevancy increased.
Abstract: Sixty young (M = 20.6), middle-aged (M = 52.4), and elderly (M = 72.6) men and women solved problems which required them to match one of two stimulus arrays to a standard. On each problem one dimension (color, form, number, or position) was relevant to correct matching, and three dimensions, which were either variable or constant, were irrelevant to solution. Age and the number of variable irrelevant dimensions were the best predictors of reaction time and error scores. Young were significantly faster than middle-aged and the middle-aged were faster than the elderly. The elderly made most errors, but the young and middle-aged were not significantly different from each other. Reaction times and errors increased as the number of variable irrelevant dimensions increased. For the elderly there was a disproportionate increase in both reaction times and errors as levels of irrelevancy increased. No reliable differences were found with regard to gender. The results were discussed in terms of an age-related decline in the ability to ignore irrelevant information.
TL;DR: Using discriminant function analysis and tests for mean differences of migrant characteristics, it was found that return migrants tend to be negatively selected on socioeconomic characteristics relative to other interstate migrants.
Abstract: Two related issues concerning aged return migration are explored in this paper. They are: (1) the common features of states that strongly attract their migration-prone native sons and daughters, and (2) what might account for the differences, if any, in the demographic and socioeconomic characteristics of return and non-return migrants. Individual characteristics of persons, age 60 and over, from the 1970 1-in-100 Public Use Sample of Basic Records were analyzed. A cluster of Sunbelt states, and Utah, strongly attract return migrants; otherwise they tend to be attracted by states which are popular destinations for aged migration in general. Using discriminant function analysis and tests for mean differences of migrant characteristics, it was found that return migrants tend to be negatively selected on socioeconomic characteristics relative to other interstate migrants. Comparisons of migrant characteristics in streams from New York and Ohio to Florida with counterstreams from Florida to New York and Ohio were consistent with a model of secondary post-retirement moves to state of birth when service and social support needs increase.
TL;DR: Systematic age exaggeration was found after age 70 in an Equadorian population noted for extreme longevity, and there was no evidence of increased longevity in the Vilcabamba population.
Abstract: Systematic age exaggeration was found after age 70 in an Equadorian population noted for extreme longevity. Extreme ages (over 100 years) were either incorrect or unsubstantiated. There was no evidence of increased longevity in the Vilcabamba population.
TL;DR: The present research suggests not only that life satisfaction is a multidimensional rather than a unidimensional construct but, of particular gerontological importance, the pattern of multidimensionality varies across age groups.
Abstract: Paralleling the increasing importance of life satisfaction and related concepts in gerontological research has been an increase in the number and kind of operational measures of these concepts. In this context the present research suggests not only that life satisfaction is a multidimensional rather than a unidimensional construct but, of particular gerontological importance, the pattern of multidimensionality varies across age groups. The analysis is based upon a national sample of the adult population of the United States in which 12 different domains of life satisfaction were subjectively assessed by each respondent. Separate factor analyses were computed for each of seven age groups. The results clearly indicate that for every age group life satisfaction is a multidimensional construct. More importantly, the dimensionally differs substantially, across the age groups -- both in the number of factors derived and the domain-specific content of those factors.
TL;DR: Relationships between Gf and Bc supported a reintegration of abilities in old age and correlations between crystallized and fluid abilities correlated more highly with performance.
Abstract: One hundred and sixty-two subjects at three age levels were tested to examine the relationship between crystallized (Gc) and fluid (Gf) abilities and three problem solving tasks varying in the abstractness concreteness of their stimuli and emphasis on past experience. It was predicted that the difference in correlations between crystallized and fluid abilities and each of these tasks would increase with increased age. The hypotheses were partially supported in the young and elderly groups of subjects. On tasks using concrete stimuli, emphasizing past experience, where no cross-sectional decline was observed, Gc (relative to Gf) accounted for an increasing proportion of variance in performance with increased age. On tasks using abstract stimuli, de-emphasizing past experience, where significant cross-sectional declines were obtained, Gf (relative to Gc) correlated more highly with performance. Contrary to previous research, relationships between Gf and Bc supported a reintegration of abilities in old age.
TL;DR: It is proposed that decreased testicular function in old age may not totally be the result of a decrement in Leydig cell steroid producing capacity, but that it may also occur due to Leydenig cell loss, possibly as the resultof age associated changes in the brain and pituitary.
Abstract: Age-related changes in testicular responsiveness to pituitary hormone stimulation were measured in Fischer rats. Suspensions of dispersed Leydig cells were prepared from the testes of groups which were 5, 12 and 29 months old. The suspended cells were challenged with 250, 750 and 2000ng Monkey-LH (LER 1909-2) for two hours and the medium subsequently assayed for testosterone. Concentrations of the hormone were determined per million cells in suspension. Besides measurement of testosterone production by each age group, pituitary and plasma LH, FSH and prolactin, and plasma testosterone were also assayed by radioimmuno-technique. Total testis weight increased in the oldest animals as the result of a high incidence of gonadal pathology. If tumorous tissue was excluded, however, testis weight fell for this group. Also, significant decreases in Leydig cell number were apparent in 12 and 29-month-old rats. Basal testosterone production, on a per million cell basis, however, was not significantly differnet in young and middle-aged rats, nor was the change in the amount of steroid produced by LH stimulation of the isolated Leydig cells. Seminal vesicle weight, prostate weight and serum testosterone decreased with age. Similarly, pituitary LH and FSH concentration decreased, but pituitary prolactin increased. Histological changes and pituitary hypertrophy reflected this increase in prolactin concentration. It is proposed that decreased testicular function in old age may not totally be the result of a decrement in Leydig cell steroid producing capacity, but that it may also occur due to Leydig cell loss, possibly as the result of age associated changes in the brain and pituitary.