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Biomedical subjects

A Viidik

Publications and source records attributed to A Viidik.

At least 37 records · Page 2Linked to original sources
PubMed1996

Influence of physical exercise on aging rats: II. Life-long exercise delays aging of tail tendon collagen.

Regular physical exercise has been shown to have a number of benefits compared with sedentary behaviour, such as delaying a number of aging changes and increasing the life expectancy but not the maximum lifespan. The purpose of this paper is to analyze the effects of physical exercise on the connective tissues of the body, especially systemic effects. We trained male Sprague-Dawley rats in a treadmill from the age of 5 months to 23 months. We analyzed the effects of training on tail tendons with respect to thermal stability of collagen and biomechanical properties of tendon bundles. Although tail tendons are attached to muscles, the are not weight-bearing as limb muscle tendons and can, therefore, be considered to be subjected mainly to systemic effects. The thermal stability of tail tendon collagen was significantly lower or "younger' for the trained group compared with the sedentary one. The biomechanical parameters were likewise "younger' with respect to maximum stress, although considerably stiffer compared with a 5-month-old base-line group. This suggests that there are several mechanisms, elicited by physical exercise, that act on the connective tissues. It can be concluded that life-long physical exercise has a beneficial influence on the connective tissues of the maturing and aging organism.

Aging↗
PubMed1996

Influence of physical exercise on aging rats: I. Life-long exercise preserves patterns of spontaneous activity.

Physical exercise has been shown to delay a number of aging changes and increase life expectancy but not maximum lifespan. We trained male Sprague-Dawley rats in a treadmill from the age of 5 months to 23 months. Up to this age the mortality (19%) was not different from that of the sedentary controls (16%). The body weights of the trained animals remained lower and reached a plateau, while those of the sedentary controls continued to increase. The spontaneous activity was assessed in an open-field setting every second month. Movement parameters (running distance, running speed, percentage of large and local movements), resting time and number of changes of direction were calculated. The running parameters were higher for the trained animals from the age of 12 months onwards, the relative difference increasing all the time. The resting time was lower for the trained animals, while the number of changes of direction did not change. It is suggested that this retardation of decline of spontaneous physical activity is due to a slowing of development of sensorimotor disturbances. These observations are compatible with a better preservation of cholinergic and dopaminergic activity.

Age Distribution↗
PubMed1996

Changes in the fibre arrangement of the rat incisor periodontal ligament in relation to various loading levels in vitro.

The relationship between the fibre arrangement of the periodontal ligament and the load-deformation behaviour was investigated at various loading levels. Transverse sections of the rat incisor were loaded in the eruptive direction in vitro and the deformation fixed at predetermined loads. Sections were prepared at these deformation levels. The periodontal ligaments were examined by polarized-light and scanning-electron microscopy. At the initial ("toe') part of the load-deformation curve, the periodontal fibres were gradually pulled and bent towards the direction of loading; their wavy pattern and periodic dark and bright bands became indistinct. At the next, linear part of the curve, the running direction of the fibres changed gradually until they were straightened and stretched. At the yielding part of the curve, the periodontal fibres began to rupture. Ruptured fibres adhering to the bone surface returned to their original obliquity and showed periodic dark and bright bands. The fibrous components of the rat incisor periodontal ligament thus transmit forces to bone at the linear part of the curve when the tooth is axially loaded.

Animals↗
PubMed1996

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.

Animals↗
PubMed1996

Failure of buflomedil to improve wound healing in ischaemic skin flaps.

The effect of buflomedil and isoxsuprine on the healing of ischaemic wounds was investigated using an ischaemic flap model previously evaluated on rats. The drugs were given twice daily intraperitoneally for a total of nine days starting on the day before operation. The wounds were tested biomechanically after 10 and 20 days of healing, respectively, and the length of surface necrosis on the flaps was measured after 10 days. The study showed no differences in any of the biomechanical (functional) parameters of the ischaemic wounds compared with the control groups, either after 10 or 20 days of healing. There were no differences in the length of surface necrosis on the flaps. Neither of these drugs has so far convincingly proved to be effective in the treatment of ischaemic wounds or flaps.

Adrenergic alpha-Antagonists↗
PubMed1995

The effect of hyperbaric oxygen on different phases of healing of ischaemic flap wounds and incisional wounds in skin.

Several studies have revealed a positive effect of treatment of ischaemic wounds and flaps with hyperbaric oxygen. We studied the effect of 100% oxygen (2.4 ATA) for 90 min daily on different phases of healing ischaemic and normal incisional wounds in rats. Hyperbaric oxygen on day 0-3 significantly increased almost all the force parameters of ischaemic flap wounds by 41-57% after 10 days of healing. On the other hand, when the treatment was continued until day 9 the positive effect on the wound healing was abolished. Furthermore, when hyperbaric oxygen was given on days 4-9 there was a tendency towards a decrease in the biomechanical parameters. Hyperbaric oxygen had no effect on the healing of normal incisional wounds.

Animals↗
PubMed1993

NORA--Nordic research on ageing. Functional capacity of 75-year-old men and women in three Nordic localities.

The aim of this cross-national study was to describe and compare differences in functional capacity of 75-year old people in three Nordic urban localities. As the life-expectancy at the age of 75 differs between the Nordic countries, there is reason to look for similar differences in functional capacity, taking differences in socio-demography, lifestyle, living conditions and health into consideration. In 1989-1991, 400 75-year-old men and women were selected to represent 75-year-olds in a Danish, Finnish and Swedish city. They participated in examinations which focused on functional capacity and health, where identical questionnaires, tests, and equipment were employed. The methods employed were developed from the experience gathered during previous studies of epidemiology of ageing in Glostrup, Gothenburg, and Jyväskylä. Functional capacity is the dependent variable multifactorially related to age, health, living conditions, and life style. The data collection was performed with participation rates in the interviews of 85% in Glostrup, 83% in Gothenburg, and 92% in Jyväskylä. The participation rates in the laboratory examinations were 76%, 67% and 77%, respectively. Examples of differences in socio-demographic background, lifestyle and measures of health and performance in the three localities are given. The Nordic study on physical, psychological and social capacity of 75-year-olds was performed with sufficiently standardised methods to allow a comparison of the results. Similar comprehensive cross-sectional comparative studies of the elderly people have not been performed earlier. Local and cross-national results will be published in each field separately and in combination.

Aged↗
PubMed1992

[Research on aging: biological perspectives].

Aging is a part of the continuous process from conception to death and is strongly modulated by environmental factors throughout the lifespan. Variability in functional capacity between different organs and between individuals therefore increases with aging. This review will discuss two tissues of importance for the fitness of the aging human being: connective tissue and bone. Connective tissues become stiffer with age, which can be mitigated by physical exercise. The physical-chemical stability of collagen is a precise measure for the functional age of the organism. While in the aged, the healing (formation of connective tissue scar) of uncomplicated incisional wounds is slightly impaired, the healing of ischemic wounds is endangered. The clinical observation that "simple" wounds also heal less well in the aged might be due to the presence of diseases with ischemia and other pathologies. During normal aging bone loses mass, structural continuity, and strength. When pronounced, these changes cause osteopenia and osteoporotic fractures. The age-adjusted incidence of osteoporotic fractures is increasing on account of changes in our lifestyle. Preventive efforts, with increased physical activity as the main feature, must be implemented to alter this trend. Our knowledge of the mechanisms of aging is not yet sufficient to formulate a policy containing preventive measures enabling man to achieve his maximum biological lifespan with good physical health and a high quality of life. Multidisciplinary efforts by biologists, clinicians and epidemiologists are warranted to achieve this goal.

Aged↗
PubMed1992

Ischemia in wound healing. II: Design of a flap model--biomechanical properties.

A standardized reproducible H-shaped double flap model for biomechanical testing of ischemic wounds was developed in rats. After 10 days of healing all the biomechanical parameters of the flap wounds decreased significantly, compared with normal healing incisional wounds. After 20 days of healing the extensibility as well as the most important biomechanical parameters were still significantly decreased. In part I of this study we showed that on day 1 the blood flow had decreased to 7% of the flow in normal incisional wounds, though it returned to normal on day 16. Here we show that this drop in blood flow results in a significant decrease in all the biomechanical parameters and thereby caused significant delay in the healing of the test wounds. There was no correlation between any of the biomechanical parameters and the length of surface necrosis on the flaps. These necroses thus do not necessarily reflect necrosis of the dermis, where the healing is responsible for the continuity and strength of the skin.

Animals↗
PubMed1992

Ischemia in wound healing. I: Design of a flap model--changes in blood flow.

A standardized ischemic, H-shaped, double flap model in rats was developed for investigating the influence of different factors that could potentially increase flap survival. The blood flow was measured in the flaps as well as in normal healing incisional wounds on day -1 (intact skin) and on days 1, 4, 8, and 16 by the xenon-133 (133Xe) clearance technique. The flow in normal healing incisional wounds remained the same as the flow in intact skin. The flow in the flaps, however, initially decreased to ischemic levels, but afterwards gradually increased to that of normal healing incisional wounds and intact skin. Further, the cutaneous blood flow in both the cranially and the caudally based ischemic dorsal flap was independent of the width of the flap.

Animals↗
PubMed1991

Freezing for postmortal storage influences the biomechanical properties of linear skin wounds.

Specimens for biomechanical investigations are often stored frozen between sampling and testing. Several authors have analysed the effects of freezing on a variety of intact tissues; while some have found mostly minor changes, others have reported no adverse effects. Healing wounds contain more fragile tissue components than other tissues and are therefore more sensitive to possible adverse effects. This study on rat skin wounds (healed for 10 and 20 days) demonstrates that freezing has a significant adverse influence on the mechanical properties. It is concluded that fresh tissue should be used whenever possible. In case storage in a freezer is necessary great care should be taken when designing the experimental protocol.

Animals↗
PubMed1991

The influence of age on the healing of normal and ischemic incisional skin wounds.

Experimental studies have not shown that the 'common' clinical experience, which suggests that wound healing is impaired in an old organism, is valid for healthy old experimental animals. We have developed a model in the rat for ischemic wound healing by using an H-shaped double skin flap, where the test wound is the horizontal line in the H. Our previous studies have shown that the blood flow in this wound is only 7% of that of a normally vascularized wound on the first postoperative day. Functional (biomechanical) properties of this wound are decreased by up to 67% after 10 days of healing and certain key properties by up to 64% after both 10 and 20 days. This study reports on the effect of aging, using 3- and 24-month-old rats. The 'normal' incisional wounds healed equally well in both groups. On the other hand, the ischemic wounds in the old animals were found to be impaired by 40-65% compared to similar wounds in the young animals. It is concluded that ischemia is deleterious for wound healing in old age and that one of the key elements of the clinical experience of impaired wound healing in old age is probably based on concomitant diseases in old patients, contributing to varying degrees of ischemia in the traumatized tissue.

Aging↗
PubMed1989

Effect of splinting on the mechanical and histological properties of the healing periodontal ligament in the vervet monkey (Cercopithecus aethiops).

Healing of the periodontal ligament (PDL) after extrusive luxation of two upper central incisors was evaluated when one tooth was splinted and the other left untreated. One millimetre thick, transverse sections of tooth, PDL and alveolar bone were examined in a materials testing machine. Load deformation curves were recorded and a number of mechanical properties were assessed. To eliminate the influence of differences in sizes and fibre arrangements, load values were reduced by the area and deformation values by the width of the PDL, and comparisons between splinted and non-splinted teeth were made at identical root levels 2 weeks after injury. Healing was also evaluated histologically at 1, 2, 3, 4 and 8 weeks after injury. There were no significant differences in mechanical and histological properties between splinted and non-splinted teeth, which suggests that splinting is of doubtful value in treatment of extrusive luxated teeth. The values for the mechanical properties of injured PDL had returned to 50-60% of those of uninjured PDL by 2 weeks after injury, indicating a rapid healing rate.

Animals↗
PubMed1988

The role of elastin in the mechanical properties of skin.

The elastin fibers of rat skin samples were degraded by the use of a purified preparation of elastase to which soybean inhibitor was added, preventing the collagenolytic activity of the elastase on collagen. Control experiments ascertained degradation of elastin and no effect on collagen. The mechanical properties of the skin samples were studied before and after the enzymatic treatment and differences ascribed to the degraded elastin fibers. Elastin plays a role in the mechanical behaviour of rat skin at small stress values and small deformations. Especially, the elastin fibers are responsible for the recoiling mechanism after a stress or deformation has been applied.

Animals↗