Effects of aging on luteinizing hormone release in different physiological states of the female golden hamster

Effects of aging on estrous cycles and LH release in response to luteinizing hormone releasing hormone (LHRH), castration, and estradiol benzoate were studied in the female golden hamster (Mesocricetus auratus). About 80% to 90% of female golden hamsters still cycled regularly when reaching 19–22 months of age. However, some animals showed age-induced irregularity of the estrous cycle which included an interruption of complete absence of estrous vaginal discharge. Young female hamsters (3–5 months) had significantly (p<0.01) higher basal LH concentration than old animals (19–22 months) in the morning of each stage of estrous cycle. LHRH elicited about 20–30 fold increase in serum LH concentrations in both young and old hamsters. No significant difference in LH release was observed between young and old hamsters in response to LHRH. In acyclic hamsters, the peak of LH release in response to LHRH was delayed. LHRH-induced LH release was greater in the morning of proestrus than during diestrus in both young and old hamsters. LH increase was significantly greater in the young than in old hamsters on the 13th and 15th day after castration. However, positive feedback stimulation of LH release by estradiol benzoate was the same in both young and old hamsters. These results indicate that in the female hamster, LH response to acute stimuli such as LHRH and estrogens is the same in the young as in the old animal and that circulating basal LH concentration may decrease or its degradation or clearance may increase during the aging process in female golden hamsters. Irregularity of estrous cycles in aging hamsters may be related to delayed responsiveness of pituitary LH to LHRH stimulation.     

All night spectral analysis of EEG sleep in young adult and middle-aged male subjects

The sleep EEGs of 9 young adult males (age 20–28 years) and 8 middle-aged males (42–56 years) were analyzed by visual scoring and spectral analysis. In the middle-aged subjects power density in the delta, theta and sigma frequencies were attenuated as compared to the young subjects. In both age groups power density in the delta and theta frequencies declined from NREM period 1 to 3. In the sigma frequencies, however, no systematic changes in power density were observed over the sleep episode. In both age groups the decay of EEG power (0.75–7.0 Hz) over successive NREM-REM cycles and the time course of EEG power during NREM sleep was analyzed. The decay rate of both EEG power density over successive NREM-REM cycles and EEG power density during NREM sleep was smaller in the middle-aged subjects than in the young subjects. It is concluded that the age-related differences in human sleep EEG power spectra are not identical to the changes in EEG power spectra observed in the course of the sleep episode. Therefore age-related differences in EEG power spectra cannot be completely explained by assuming a reduced need for sleep in older subjects. The smaller decay rate of EEG power during NREM sleep in the middle-aged subjects is interpreted as a reduced sleep efficiency. The results are discussed in the frame work of the two-process model of sleep regulation.     

Studies on catalase, glutathione peroxidase and superoxidismutase activities in aging cells of Paramecium tetraurelia

The nature of the aging process has been the subject of considerable speculation. Now, some data indicate that free radical reactions going on continuously in the cells contribute to aging. Considering these data, we have investigated the activity of enzymes (catalase, glutathione peroxidase, superoxidismutase) present physiologically in the cell to limit to tolerable levels, the rate of free radicals or H2O2. These enzymes activities were assayed in Paramecium tetraurelia as clonal age increased. Catalase activity increases slightly during aging of paramecia, i.e. during maturity and senescence phases (20-150 fissions). No significant changes in glutathione peroxidase and superoxidismutase is found. Catalase activity was also assayed as a function of culture conditions. As the cells begin starving and the percentage of autogamous cells increases, catalase activity decreases. After autogamy, a large increase of catalase activity occurs during the sexual immaturity phase, i.e. during the first 20 fissions. By another way, H2O2 added in the culture medium (from 0 to 15 X 10(-5)M) causes an important increase of catalase activity (from 100 U.I. to 250 U.I.). The possible role of O-.2, OH. and H2O2 in aging is discussed.     

Effect of Fatiguing Exercise on Longitudinal Bone Strain as Related to Stress Fracture in Humans

Muscular fatigue in the training athlete or military recruit has been hypothesized to cause increased bone strain that may contribute to the development of a stress fracture. Under normal circumstances, muscles exert a protective effect by contracting to reduce bending strains on cortical bone surfaces. In vivo strain studies in dogs show that muscle fatigue following strenuous exercise elevates bone strain and changes strain distribution. However, a similar experiment has yet to be performed in humans. The purpose of this work was to test the hypothesis in humans that strenuous fatiguing exercise causes an elevation in bone strain. It was also hypothesized that this elevation is greater in younger people than in older people due to the decline in muscle strength and endurance that normally occurs with age. To test these hypotheses, strain in the tibiae of seven human volunteers was measured during walking before and after a period of fatiguing exercise. Neither hypothesis was sustained. Post-hoc analysis of the strain data suggests that strain rate increases after fatigue with a greater increase in younger as opposed to older persons. Although not conclusive, this suggests that it is strain rate, rather than strain magnitude, that may be causal for stress fracture. © 1998 Biomedical Engineering Society. PAC98: 8745Dr, 8745Bp, 0180+b     

Aβ40 is a major form of β-amyloid in nonhuman primates

Because aged nonhuman primates show β-amyloid (Aβ) deposition in senile plaques and blood vessels similar to that seen in human aging and AD, we used C-terminal specific antibodies to Aβ₄₀ and Aβ₄₂ to investigate Aβ peptide length in the brains of 11 aged rhesus monkeys and a 59-year-old chimpanzee. In contrast to AD, where the earliest and most prominent form of Aβ in senile plaques is Aβ₄₂, in the monkey, Aβ₄₀-positive plaques predominated. The ratio of Aβ₄₎: Aβ₄₂-positive plaques averaged 2.08 in the monkey, as compared to a mean ratio of 0.37 in 68 human AD subjects (p < 0.001). Aβ₄₀ was also more prominent in the chimpanzee than in humans. Possible explanations for these findings include species differences in the cleavage of Aβ from the amyloid precursor protein or in the activity of a putative carboxy peptidase forming Aβ₄₀ from Aβ₄₂ in situ.     

AN ELECTRON MICROSCOPIC EXAMINATION OF AGE-RELATED CHANGES IN THE RAT LIVER. The Influence of Diet

The influence of age and diet on the ultrastructure of hepatocytes is reported. The following dietary manipulations were investigated: Group 1, fed ad libitum a diet containing 21% protein; Group 2, fed a similar diet but restricted to 60% of the intake of Group 1 from 6 weeks of age onwards; Group 3, restricted from 6 weeks to 6 months of age and thereafter fed ad libitum; Group 4, restriction started at 6 months of age; Group 5, fed ad libitum a diet containing 12.6% protein. In all groups the size of hepatocytes was found not to increase during adult life. The size of hepatocytes in Groups 2 and 4 was the same as or larger than that of the other groups; thus food restriction resulted in a decreased number of hepatocytes. Changes in the structure of some organelles and the accumulation of lipofuscin granules occurred with advancing age and the extent of these age-related changes was less in Groups 2 and 4 than in the other groups. These morphologic findings in conjunction with our previously reported metabolic findings provide a new view of the action of food restriction on the aging process. ACTA PATHOL JPN 38: 1119∼1130, 1988.     

Regional changes in monoamine metabolism in the aging constant estrous rat

Studies were undertaken to determine levels of monoamines and their metabolites in brain regions in young (3–4 months) normally cycling and old (25–26 month) constant estrous female rats. Dopamine (DA) concentrations were reduced in old rats in the median eminence (ME), medial basal hypothalamus (MBH), preoptic area-anterior hypothalamus (POA-AH) and the striatum. Similarly, concentrations of dihydroxyphenylacetic acid (DOPAC), the major acid metabolite of DA, were reduced significantly in all 4 regions. In the ME, a strong positive correlation was observed between DA and DOPAC concentrations in both young and old rats. Concentrations of norepinephrine (NE) were reduced in old rats in the MBH and POA-AH but not in the ME or striatum. Concentrations of serotonin (5HT) and its major metabolite, 5-hydroxyindoleacetic acid (5HIAA) were generally unchanged with age in all of the regions examined. These studies indicate the age-related regional alterations in DA and 5HT metabolism can be monitored by methods which quantitate monoamines and their metabolites.     

Normal aging decreases regional homogeneity of the motor areas in the resting state

Our knowledge about aging modulation of the central motor system remains sparse and contradictory. In the current study, we used functional MRI (fMRI) to study the aging influence on regional homogeneity of the motor-related brain areas in the resting state. We found that regional homogeneity in extensive motor regions, like the cingulate motor area, cerebellum, primary motor cortex, premotor area, supplementary motor area, thalamus, globus pallidus and putamen was significantly decreased in aged subjects. Our study indicates that normal aging process may disrupt the function of motor areas in the resting state, which may contribute to the declined motor ability in aged population.     

Age-dependent changes in the susceptibility to apoptosis of peripheral blood CD4+ and CD8+ T lymphocytes with virgin or memory phenotype

Susceptibility to apoptosis changes with age and most of the available data on lymphocytes refer to mitogen stimulated cells. We studied this susceptibility in quiescent, purified CD4+ or CD8+ T cells from a group of Italian old people compared with a group of young people. We found that an apoptotic agent such as 2-deoxy-D-ribose (dRib), which acts via glutathione depletion and oxidative stress, was more effective in CD4+ T cells from young donors, while no difference was found in CD8+ T cells. On the contrary, another agent such as TNF-alpha, which acts via receptor engagement, was more effective in CD8+ T cells from old subjects, and no difference was found in CD4+ T cells. When marker of activation-memory were investigated, no difference between young and old subjects was found when dRib was used. Differently, when TNF-alpha was used, memory and activated CD4+ T cells from old donors were less sensitive than younger counterparts, while memory CD8+ T cells from old donors were more sensitive than younger counterparts. This suggests that age-related changes in susceptibility to apoptosis of resting T cells largely depend on the type of the apoptotic stimulus which is used as well as on the memory phenotype of the cells. These results may also account, at least in part, for the deep remodelling of T cell repertoire that occurs during ageing.     

Age changes in geometry and mineral content of the lower limb bones

Subperiosteal expansion and increase in second moments of area with aging of eleven femoral and tibial cross-sections are documented in a large archaeological sample from the American Southwest. In contrast to these geometric changes, we found little change with age in bone mineral density measured using photon absorptiometry. Thus, the most significant structural changes with age in bone appear to involve its geometry and material characteristics other than its density. Variation in age-related geometric remodeling between cross-section locations and populations may be caused by differences in mechanical stress and strain levels in vivo in the lower limb.