Cognitive processes involved in the evaluation of life satisfaction: implications for well-being.

Extensive research has been conducted on the level and the predictors of well-being in old age, but less is known about the cognitive processes used by the aging individual to evaluate life satisfaction. To investigate the relationship between well-being in the present and in previous decades in life and explore the cognitive processes involved in these evaluations, 203 old participants aged 70-85 years were interviewed and their level of present life satisfaction and depressive symptoms was measured. One year later, depressive symptoms were recorded for a follow-up sample of 65 participants. The results showed that evaluating old age as the best part of life was related to increased well-being. Evaluations of positive periods in life were based on general positive qualities, whereas specific negative events were given as reasons for nominations of negative periods in life. Deviations from this general pattern were related to lower levels of well-being. Use of comparison strategies to evaluate present life satisfaction was frequently reported, and the use of temporal comparisons was predictive of changes in depression over a one-year period. The present study indicates that the cognitive processes used in the evaluation of life satisfaction are related to present and future well-being.

Effects of age on the stress-strain and stress-relaxation properties of the rat molar periodontal ligament.

OBJECTIVE: We examined the stress-strain and stress-relaxation properties of the periodontal ligament (PDL) in the rat molar at 2, 6, 12, and 24 months of age to elucidate age-related changes in the tooth support function of the PDL. DESIGN: From the dissected left and right mandibles in each rat, a pair of transverse sections (ca. 0.45 mm in thickness) of the first molar was cut at the middle part of the mesial root. We then obtained a load-deformation curve for the PDL, using one of the paired sections. The other section was loaded to as much as 50% of the maximum load as determined from the contralateral section, and keeping the deformation constant for 10 min, a load-relaxation curve was obtained and analysed. RESULTS: The maximum shear stress and tangent modulus decreased between 2 and 24 months of age. As the maximum shear strain increased with age (P < 0.001), the failure strain energy density did not change between 2 and 24 months of age. The stress-relaxation during the 10 min period decreased from 2 to 24 months of age (P < 0.01). The relaxation process of the PDL in each age was well described by a sum of three exponential decay functions. The age-related decrease in the relaxation was found to be mainly due to the increase in the relaxation time for the long-term relaxation component. CONCLUSION: These results indicate that the maximum shear stress and stiffness of the rat molar PDL decrease between 2 and 24 months of age; but its toughness remains unchanged due to an increase in the extensibility. Our findings further indicate that the fluid flow and movements of macromolecules within the stretched PDL fibres during the stress-relaxation decrease with advancing age.

Age-related and regional differences in the stress-strain and stress-relaxation behaviours of the rat incisor periodontal ligament.

Groups of rats were killed at 2, 6, 12, and 24 months of age. From dissected left and right mandibles in each rat, three pairs of transverse sections were cut at the incisal, middle, and basal regions of the incisor. One section in each pair was loaded until failure and a stress-strain curve for the periodontal ligament (PDL) was obtained. The other section was loaded to up to 50% of the maximum shear stress as determined from the contralateral section and then kept at a constant strain for 10 min, to obtain the stress-relaxation curve at the same region of the PDL. The maximum shear stress and toughness increased with age at the incisal region and the maximum shear strain increased with age at the incisal and middle regions. The tangent modulus decreased with advancing age at the middle region. The stress-relaxation during 10 min decreased with advancing age at the incisal and basal regions, but not at the middle region. The relaxation process was well described by a sum of three exponential decay functions, reflecting the short-, medium-, and long-term relaxation components. The age-related decrease in the relaxation was mainly attributable to increases in the ratio and relaxation time of the long-term relaxation component. These results suggest that with advancing age the mechanical strength and toughness of the PDL are enhanced mostly at the incisal region and that the viscous fraction is relatively decreased at the incisal and basal regions along the long axis of the rat incisor.

Voluntary and forced exercise influence the survival and body composition of ageing male rats differently.

The importance of maintaining physical fitness by engaging in exercise in a life-long perspective as well as the avoidance of obesity has been emphasised in recent years by epidemiological studies on human populations as well as studies on laboratory rodents. In laboratory studies, voluntary running in wheels and forced training in a treadmill have been used with beneficial results. Restriction of the food intake of sedentary laboratory rodents can be regarded either as life prolongation or prevention of life shortening by obesity. We compared the effects of these interventions on male Sprague-Dawley rats from the age of 5 to 23 months in the following groups: (1) RW=voluntary running in wheels; (2) PW=fed to pair weight with RW animals; (3) TM=forced training in a treadmill; and (4) S1=sedentary with ad libitum access to food. Each group consisted of 32 animals, all housed individually in cages. Two RW animals died, five died in each of the PW and S1 groups and 10 in the TM group (p<0.05). The S1 and TM groups gained most weight, the TM less after the age of 21 months (p<0.05). The body weights of the RW group was lower than those of the S1 and TM groups all the time (p<0.001) and the difference increased all the time. Body composition was analysed by bioelectrical impedance analysis. There were no differences in fat free mass (FFM) neither between RW and PW at any time, nor between S1 and TM. FFM was lower for RW and PW compared to S1 and TM. TM gained FFM until the age of 17 months, while S1 gained FFM all the time. S1 gained fat all the time, but the gain for TM levelled off. It stayed constant for RW until 13 months and decreased afterwards. We conclude that voluntary running in wheels enhances survival and keeps body fat lower than in PW animals up to the age of 17 months. Body composition and survival data suggest that voluntary running is more optimal than forced. Care must, however, be taken in analyses, since RW is a heterogenous group because there is a large variation between the animals with respect to how much they run.

The influence of dressings on the healing of normal and ischaemic wounds and flap survival.

The effects of dressing with Duoderm (occlusive hydrocolloid) and Mepore (permeable viscose) on the healing of normal and ischaemic incisional wounds, and on flap survival, were investigated in 60 rats. The biomechanical properties of dressed normal wounds after 14 days did not differ from those of the undressed controls. In contrast, energies at maximum and breaking (load*S, stress*S) of dressed ischaemic wounds decreased by 30%-42% after 14 days of healing, compared with undressed ischaemic controls. Dressing decreased the shrinkage of ischaemic wounds and necrosis length of ischaemic flaps. Normal incisional wounds can safely be dressed for 14 days without the wound strength being affected. Dressings may be useful clinically in preventing superficial dermal necroses. One must, however, be aware of the impairment of the wound strength of ischaemic incisional wounds.

Experimental gerontology in the Nordic countries.

Research in geriatric medicine developed in the Nordic countries in the 1950s, following the tradition from the United Kingdom. Quite early, longitudinal epidemiological studies of 'normal' ageing emerged. Now there are chairs in geriatric medicine at many of the medical schools. Experimental gerontology came much later, typically scattered in a variety of medical school departments. There is only one chair in gerontology (in Tampere). Two major research undertakings have emerged in recent years, the Danish Centre for Molecular Gerontology, and a cluster of research groups at the Division of Geriatrics at the Karolinska Institutet. Other research groups are found in Denmark at the universities in Aarhus, Copenhagen and Odense; in Finland at the universities in Jyväskylä, Kuopio, Tampere and Turku; and in Norway at the university in Trondheim. These activities are reviewed country-wise.

Housing conditions influence the survival and body composition of ageing rats.

Ad libitum fed male Sprague-Dawley rats were randomly assigned to be housed individually (n=32) or four in each cage (n=32) from five to 23 months of age. Body weight and body composition by bioimpedance analysis were monitored longitudinally. An equation for analysis of body composition was developed. Deaths and causes of death were recorded. Of the individually housed animals (H1) 16 percent died, while 44 percent of those housed four in a cage (H4) died, the most common causes of death being circulatory failure, nephritis and tumours of the hypophysis.Body weight increased in both groups over time, significantly more for H4 from 6months of age. Both fat free mass and total body fat increased in both groups over time. Fat in percent of body weight increased up to an age of 14months. H4 animals had significantly more fat from 11 to 20 months of age but lost weight, mostly fat when approaching 23months of age. The occiput-sacrum length of the animals increased up to 11months of age and stayed then constant. Animals in both groups grew also in the cross-sectional dimension. The H1 animals continued to grow all the time, while the growth of the H4 animals stopped at the age of 17 months, when the mortality started to become pronounced. It is concluded that housing conditions can modulate the outcome of the ageing of sedentary and otherwise not treated rats in long-term experiments. Further, the feasibility of monitoring body composition longitudinally with bioimpedance analysis was demonstrated.

Does long-term physical exercise counteract age-related Purkinje cell loss? A stereological study of rat cerebellum.

Physical exercise affects properties of the central nervous system that may increase the brain's ability to counteract degenerative changes. We have previously reported that rats trained from 5 to 23 months of age have less age-related decrease in spontaneous motor activity than sham-treated sedentary rats. Each rat ran at a speed of 20 m/min on a horizontal treadmill, for 20 minutes, two times per day, 5 days a week. In the present study we have carried out stereological analyses of the cerebella of the same rats. The total number of Purkinje cells was estimated with the optical fractionator technique, the local volumes of individual Purkinje cells with the planar rotator technique, and the volumes of the cerebellar layers with Cavalierìs principle. We found that sedentary aged rats have 11% fewer Purkinje cells and 9% smaller Purkinje cell soma volumes (both 2P = 0.02) than exercised aged rats, and that exercised aged rats have the same number of Purkinje cells as young rats. These findings indicate that the degree of age-associated degenerative changes in parts of the central nervous system is dependent on earlier life style and health habits and may be prevented or delayed by physical exercise.

The collagen biomarker of aging can be influenced by physical exercise also in senescent rats.

The normal processes of aging lead gradually to impairment of the function of most organs and to a gradually increasing force of mortality. This can to some extent be counteracted by life-long physical exercise as evidenced by epidemiological studies. The same is seen in animal experiments, where the mean survival time but not the maximum lifespan is increased by life-long physical exercise. In previous studies we have shown that the with aging increasing thermal stability of collagen-a biomarker of aging-is slowed down by life-long physical exercise in male Sprague-Dawley rats. Here we investigate whether late onset physical exercise also has a beneficial effect on this biomarker of aging. We found that mild exercise (100m/day in a treadmill) retards the increase of thermal stability of collagen, when the rats are trained from 27 to 30 months of age. On the other hand more extensive exercise (400m/day from 24 to 27 and 200m/day from 27 to 30 months of age) has the opposite effect, which is in agreement with our previous study on rats trained from 12 to 24 months of age. We conclude that senescent rats can also benefit from physical exercise and that the optimum amount of training decreases with age.

Comparison between continuous and intermittent physical exercise on aging rats: changes in patterns of spontaneous activity and connective tissue stability.

Life-long physical exercise increases the mean but not maximum life span of laboratory rodents. It further improves the performance in an open field setting, which suggests a delay of sensorimotor disturbances, and retards the aging increase of thermal stability of collagen. The purpose of the present study was to examine whether the amount or continuity of training is more important. We trained male Sprague-Dawley rats for 12 months from the age of 12 months in a treadmill: 1) continuously for 3 km/week (total distance covered: 144 km); 2) intermittently for 3 km/week for 8-week periods with 8-week resting periods in between (72 km), and 3) intermittently for 6 km/week for 8-week periods with 8-week resting periods in between (144 km). All training regimens prevented the increase in body weight seen in sedentary animals, although the intermittent training programs caused fluctuations with the training and resting periods. With respect to spontaneous movements in an open field setting, continuous training was most effective in counteracting age-related changes. Continuous training was also most effective for delaying age-related increase in thermal stability of collagen. We conclude that the continuity of training is more important than the amount and intensity of training.

The biological aging is our inescapable fate--but can we modify it?

The quest for postponing ageing has been in the mind of man since the earliest civilisations and the ancient symbols (healing water, herbs, sleep and the snake) are also found in the attempts undertaken today. Maximum life span, however, has not changed much due to these efforts. The rate of increase has been estimated to be about 10 year per million years. Mean life span has, on the other hand, increased dramatically, due to major environmental improvements, from about 30 to 80 years. Much of this increase is due to decrease in childhood and early adulthood mortality and has occurred during the last 130 years. Whether and to what extent this increase will continue is not clear. The complexity of the human genome is discussed together with current knowledge of gene technology and ethical problems in this context. Life extension in primitive animals with much simpler genomes, and inheritable diseases with premature ageing in man are used as examples for how new knowledge can be gained in this field. Transgenic animals and knockout mice are used as examples for progress in gene technology. It is emphasised that at present the best possibilities to ameliorate the effects of the ageing processes are having a healthy lifestyle, which includes a balanced diet, avoiding being overweight, drinking some red wine and doing a moderate amount of physical exercise.

Influence of physical exercise on aging rats. III. Life-long exercise modifies the aging changes of the mechanical properties of limb muscle tendons.

We have previously shown that long-term regular physical exercise has a systemic influence on the rat by slowing the aging of its connective tissues, measured as thermal stability and biomechanical properties of tail tendons. This paper analyses whether the properties of limb muscle tendons are influenced not only by the aging process and the systemic effects of exercise but also from direct mechanical stimuli from long-term physical exercise. Male Sprague-Dawley rats were trained in a treadmill from the age of 5 to 23 months. The effects of training on muscle tendons were analyzed with respect to biomechanical properties. Also, the viscoelastic activation energies for interactions between collagen and the proteoglycan gel as well as between collagen fibrils were measured. Finally the asymptotes from the creep curves were calculated in order to estimate the magnitude of the viscoelastic creep. The effects of aging were analyzed with respect to the same parameters by comparing the group of 23-month-old sedentary rats with a 5-month-old baseline group. The biomechanical parameters did not change significantly with physical exercise. Neither did the activation energies change, but the asymptotes of the creep curves decreased, showing that there was less viscoelastic creep. Aging rendered the tendons significantly stronger and stiffer, increased the energy-absorbing capacity and decreased the strain values. The activation energies did not change with aging, but the high creep curve asymptote for the flexor tendons decreased. We conclude that aging rendered both types of tendons stiffer, and decreased their strain values at breaking point. Aging also increased the stress value, the energy absorption and the dry weight for the flexor tendon. Further, while physical exercise has a systemic delaying effect on age changes in connective tissues, in tendons subjected to substantial mechanical loads this effect as measured with biomechanical methods is counteracted by the optimization process elicited by the same physical exercise.

The influence of occlusive dressing and hyperbaric oxygen on flap survival and the healing of ischaemic wounds.

The effect of dressing with Duoderm (hydrocolloid) and treatment with hyperbaric oxygen was investigated on the healing of ischaemic incisional wounds and on flap survival in rats. After 10 days, Duoderm dressing of ischaemic wounds decreased all strength parameters (load*S, stress*S) by 41%-44% and the improvement of ischaemic wound healing by hyperbaric oxygen treatment shown in our previous study was not seen. After removal of Duoderm on day 10 the biomechanical properties had improved but not returned to normal on day 20. In the dressed animals the shrinkage of ischaemic wounds and the extension of necrosis on the ischaemic flaps were reduced. Dressing may be useful clinically in preventing superficial dermal necroses. One must, however, be aware of the impairment of the wound strength of the incisional wounds.

The effect of recombinant basic fibroblast growth factor (bFGF) in fibrin adhesive vehicle on the healing of ischaemic and normal incisional skin wounds.

Normal and ischaemic incisional wounds in rats were treated with recombinant human basic fibroblast growth factor (rbFGF) in fibrin adhesive vehicle. After 10 days of healing the maximum load*S and stress*S (S denotes correction for shrinkage) of ischaemic wounds were increased by 45% and 39%, respectively, after treatment with 20 micrograms rbFGF and by 67% and 56% after treatment with 60 micrograms rbFGF. After 20 days only 20 micrograms rbFGF had any effect and increased maximum load*S by 31% and energy at maximum (load*S, stress*S) by 40%-48%. In normal wounds 0.6-20 micrograms and 60 micrograms rbFGF decreased the strength parameters by 19%-34% and 49%-52%, respectively, after 10 days. After 20 days there was no negative influence but 60 micrograms rbFGF increased the biomechanical properties by 15%-24%. Treatment with the fibrin adhesive vehicle alone decreased the biomechanical properties of ischaemic wounds after 20 days, and of normal wounds after both 10 and 20 days. In conclusion, rbFGF can improve the healing of ischaemic wounds and may be used in the treatment of ischaemic wounds in patients, but it can have negative effects on normal wound healing.

Diclofenac and indomethacin influence the healing of normal and ischaemic incisional wounds in skin.

The influence of diclofenac and indomethacin on the healing of normal (non-ischaemic) incisional wounds, and of ischaemic incisional wounds using a flap model, was studied in 192 rats. Both drugs improved the strength of normal wounds as the energies at maximum load and stress increased by 23% - 33% after 10 days. After 20 days the treated normal wounds were stiffer. In ischaemic wounds neither drug influenced the biomechanical properties after 10 days, which reflects the healing of the deep dermis, but both countered the ischaemia of the superficial skin as the necroses on the skin flaps decreased. After 20 days the drugs decreased some of the strength parameters of ischaemic wounds, indomethacin in particular, which decreased these parameters by about 20% - 35%. In conclusion, in certain doses the drugs improved the healing of normal wounds. The healing of ischaemic wounds was unaffected after 10 days but decreased after 20 days. The drugs may, however, be used for reducing superficial necroses of skin flaps.

Influence of physical exercise on old rats: changes in patterns of spontaneous activity and connective tissues.

It has been shown that life-long, regular physical exercise has benefits for humans as well as laboratory animals. Population studies have shown that the longevity of humans is increased due to the decrease in all-cause mortality. Further, the functional capacities of organ systems, especially the cardiovascular, are maintained better. Body fat content stays lower. Similar conclusions have been drawn from animal studies, most of them using voluntary exercise in running wheels. We have previously shown that spontaneous activity, measured in an open field setting, is better preserved, suggesting a slowing of sensorimotor impairment with age, and possibly improved maintenance of dopaminergic and cholinergic systems. Further, the systemic effect on connective tissues was a slowing of the age-dependent increase of stability by changes in the cross-linking patterns. The purpose of the present investigation was to analyze whether late-onset training programs had any such effects, i.e., whether the aging effects seen in sedentary animals could be reversed to some extent. We trained male Sprague-Dawley rats from the age of 18 and 20 months until the age of 22 months, i.e., for 4 and 2 months, in a treadmill for 800 m/day. Spontaneous activity in an open field was assessed at the ages of 18, 20, and 22 months. For systemic changes in connective tissues, tail tendons were analyzed with respect to thermal stability and biomechanical strength parameters. The rats trained for 4 months lost weight significantly, which suggests that most of the fat accumulated during a sedentary life can be removed by physical exercise. Two months of training, either from the age of 18 or 20 months, had a positive effect on spontaneous activity, while the last 2 months of a 4-month training period had a negative influence. We conclude that the exercise program was too strenuous to be maintained for 4 months, which should be interpreted as a failure to increase the functional capacity sufficiently. Analysis of the thermal stability and biomechanical properties showed that both training programs moved these properties in a "younger" direction. We conclude that training starting late in life also influences the aging rat in a positive way, although there are limitations to the intensity of training that is beneficial.

Effect of delayed primary closure on the healing of ischemic wounds.

OBJECTIVE: To study the influence of delayed primary closure on the healing of ischemic wounds in rats. METHODS: Wounds sutured after a delay of 3 days were compared with primary closed wounds by biomechanical testing. RESULTS: The delayed wounds were as strong as primary closed wounds when tested 10 days after wounding. Thirteen days after wounding (10 days after closure), nearly all the biomechanical parameters of the delayed wounds were increased, compared with those of primary closed wounds that had healed for 10 days. The wounds closed after a delay were weaker, however, when tested 20 days after wounding. CONCLUSION: An ischemic wound can safely be left open for 3 days before suturing, i.e., for prevention of infection in contaminated wounds, without affecting the biomechanical properties at the time of removing the sutures, which is often performed clinically 10 to 12 days after the operation.

The impact of ischemia on wound healing is increased in old age but can be countered by hyperbaric oxygen therapy.

The healing of normal incisional wounds and ischemic flap wounds was investigated in young (10 weeks) and old (102-104 weeks) rats, together with the effect of treatment with hyperbaric oxygen on day 0-3 of healing. After 10 days of healing all biomechanical strength parameters of normal wounds were decreased by 30-40% and of ischemic wounds by 40-51% in the old animals compared with the young controls. After 20 days all strength parameters of normal wounds and ischemic wounds were decreased by 29-37% and 46-58%, respectively, in the old rats compared with those of the young ones. Treatment with hyperbaric oxygen of ischemic wounds in old animals increased all strength parameters by 36-50% after 10 days and by 67-88% after 20 days. For young animals, the corresponding increase was only 21-35% after 10 days and no effect was seen after 20 days. The shrinkage of ischemic wounds was decreased by 48% in the old animals compared with the young ones. It can be concluded that ischemia intensifies the impairment of the healing seen in old age. On the other hand, treatment of ischemia with hyperbaric oxygen is much more effective in old animals, despite the fact that it also has a pronounced effect in young animals. Furthermore, the results suggest a decreased wound contraction with age.