Biomedical subjects
Publications and source records attributed to A Kment.
The central question in the field of experimental gerontology is: what is biological aging? It is true that a living body must obey the laws of causal determinism; like all bodies it is subject to the physical and chemical laws of the phenomenal world. But there is a further aspect; as well as the finality which unites the part, the organism and the organ, there is also a metaphysical meaning at work in life.
From birth to death life represents a structural connection of events, regardless of the space of time separating them. The potentiality of a living system is a finite one. It can only be finite since infinity cannot be achieved by a progression of finite elements. Ontogenesis then ends when the potentiality of the organism is fully realized and has reached an optimum, the highest level of bionomical order (Kment, in prep.), which corresponds to the vitality maximum (Beier, 1980). In attacking the problem of probability statements in their most general form, Popper (1959) developed the "propensity interpretation of probability". In my opinion, the disposition towards aging, or, in other terms, the propensity of biological aging, also has to be regarded as a reality--as a biological reality. Since the propensity of aging is viewed as a measure of a disposition, we also have to deal with two questions in order to accept it as a biological reality: Is there any measure of biological aging which can be defined operationally? Is there an operational definition possible of the propensity of biological aging? The acceptance of the concept of propensity in biomedical gerontology, will make it necessary to comment anew on the unsolved problem of a general definition of aging.
UNLABELLED: Following injection of hydralazine, a benign coronary-artery-dilating drug, myocardial blood flow increased by 25%. Myocardial 201-thallium uptake at rest and after intravenous injection of 12 mg hydralazine was quantitatively investigated in 28 patients. In patients with essential hypertension or coronary artery stenoses of up to 90%, myocardial 201-thallium uptake increased by 19%-30% in nonischemic areas. In 9 of 14 patients with regional imaging defects, thallium uptake also increased in these ischemic areas; 4 of these patients had asynergies in the area of imaging defects. In 3 patients with a complete obstruction of a major branch of a coronary artery perfusion defects developed following hydralazine application. CONCLUSION: An increased 201-thallium uptake in an ischemic area indicates reperfusion; this could be helpful for deciding whether coronary surgery should be performed or not.
We investigated the alteration of the ACE in different parts of the circulation in 21 patients with essential hypertension, who suffered from angina pectoris attacks. Blood samples were taken during diagnostic cardiac catheterisation. The ACE was fluorimetrically measured and compared to 48 normotensive patients. In 11 patients the Plasma Renin Activity (PRA) was additionally determined by means of bioassay. The ACE was significantly (p less than 0.001) elevated in all investigated regions but a different distribution was not observed. We found a positive correlation between the ACE from the left ventricle and the systolic, mean arterial and diastolic blood pressure. Furthermore, we observed a negative correlation between ACE and PRA. No relationship could be calculated between ACE and electrolytes, creatinine or haemodynamic parameters. Our results indicate that the ACE may contribute to the pathogenesis of so-called essential hypertension.
In the course of a long-term cohort study of stress and aging, the spontaneous activity of 169 male Sprague-Dawley rats was measured at various ages from 9 to 30 months. 84 animals were submitted to crowding from the age of 5 months onwards by housing them in groups of 12 per Makrolon-IV cage. 85 rats, kept as usual in groups of 6 per makrolon-IV cage, served as a control. Spontaneous activity was assessed by an electronic instrument (Animex Activity Meter), which also enabled us to distinguish between total and large movements. During senescence, the spontaneous activity of the control animals decreased slightly by approximately 20% after the age of 18 months. In addition to the quantitative change, a progressive flattening of the activity rhythm was observed. The animals kept under crowded conditions did not reveal any age-related decrease in spontaneous activity. At an advanced age, this resulted in significantly higher activity values in the crowded group as compared with the controls. The differences appeared even earlier and seemed to be more pronounced in the number of large movements. However, the progressive disappearance of the endogenous rhythm was apparent in both the crowded and the control group. It can be concluded that at least two types of change in the central nervous system may be responsible for the aging-changes in spontaneous activity: one which disintegrates the "time structure" of the organism, and a second one which affects motivational centers. Crowded conditions seem to improve the latter, whereas they have no effect on the aging of the "biological clock".
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In experimental gerontology as a biomedical science, the knowledge and understanding of aging is expressed in hypotheses, theories and models. In this context, the model turns out to be a specific criterion of a definite level of abstraction. The general concept of models comprehends three characteristics: illustration, reduction and pragmatism. Every model is an approximating attempt to comprehend reality. In experimental gerontology various kinds of models can be used. This variety is necessary result of the variety of methods used in this field of science. Any reductionism would imply a restriction, limitation and rigidity. The final aim of experimental gerontology should be the evaluation of a universal dynamic model of aging which is valid for any aging process in biological systems.
Sprague-Dawley rats aged 6 to 22 months were stressed for 2, 16 and 9m resp. by the influence of noise (106 dB, 2h/d) and overcrowding (12 rats/Makrolon-IV-cage). Parameters of the plasma, brain, testicles and the liver (enzymes, metabolites and hormones) and well-known age parameters were evaluated to obtain objective criteria for stress influences. The weights of the whole body and some organs were also measured. The most distinct changes were seen in the plasma enzyme activities CPK, ALD, CHE and AP, in the concentrations of CHO and TRG and in the levels of testosterone, corticosterone and aldosterone. The contraction-relaxation of the tail tendon and the soluble collagen of the corium changed in the direction of higher age, just as lipofuscine content in the brain, cerebellum and the adrenals did. Some activities of enzymes and concentrations of metabolites changed in the brain, liver the testicles. Adrenal weights rose sharply in both stress groups; the body weight was lower. There were some differences in the effects of the two stress factors. These investigations gave some information about the relation between stress and aging and provide a simple means of determining the influence of stress.
The influence of noise and overcrowding on the learning ability and memory was investigated during a long term cohort study in 120 male Sprague Dawley rats covering an age range from 8 to 14 months. The investigations were performed by means of a semi-automatical multiple-T-maze with 7 choice points. The results showed that noise and overcrowding enhanced the learning ability and memory in rats up to an age of 10 to 12 months. However, the learning ability and memory were declining faster with age in the stressed animals than in the unstressed ones. The stressor "overcrowding" proved to be more effective than the stressor "noise" applied by the authors.
The capacity of age parameters to discriminate between groups or individuals of different biological age was investigated in the course of a long-term cohort study. 23 age parameters measured in 71 male Sprague-Dawley rats at the ages of 10, 17, 25 and 30 months, were submitted to a stepwise discriminant analysis. An optimal simultaneous discrimination between the four age groups was obtained by 3 discriminant functions with scores of 89.8%, 6.2% and 4%, with a correct classification of 98,6% of all individuals. Three analyses of successive age groups (10--17, 17--25, 25--30 months) resulted in a 100% correct classification by one function each. However, it turned out that in different phases of senescence an optimal discrimination between individuals or groups of different biological age is obtained by distinct combinations and weights of the parameters.
Biological age may be defined at the state of the organism as a whole which is characteristic of the respective chronological age. Usually, it is estimated by multivariate analysis of a battery of age parameters. However, this procedure requires the knowledge of the regularities of multicellular ageing since interferences about the behaviour of the total system from its subsystems may only drawn when the regularities of the total system are understood. By means of the ageing of the rat, the possibility is demonstrated to study these regularities by factor analysis. As a result, primary and system-specific secondary aging processes are postulated which are expressed to various extents in the individual age parameters.
Experimental gerontology is changing progressively from an idiographic (descriptive) science to a nomothetic (conceivable in terms of laws) one. Besides the punctual studies of the total complex of aging, those investigations will acquire increasing significance which take into account the bionomal character of life. In addition, the views of logic science, epistomology and system theory will be employed in experimental gerontology more often than is the case now. Experimental gerontology will finally lead to the development of a theoretical gerontology.
Applying the research methods used in natural sciences and medicine and the concept of bionomy, it has been attempted to make basic statements about the process of aging. 140 geriatric agents have been examined with reference to the medications for their use, their connection with the aging process and particularly their effect on vitality. Finally it has been pointed out that test procedures for age parameters in experimental and clinical gerontology, which can be used in assessing geriatric agents, are in existence.
We tried to develop a model of in-vivo investigations into the DNA repair capacity of rats and, by means of this model, to determine the effect of age. To this end the DNA repair capacity was determined after gamma-irradiation with 3 groups of male white Sprague-Dawley rats aged 6, 18-20 and 32-34 months. The organs liver, kidney, heart and spleen were used for this investigation. The relative repair (RR) showed a discontinuous course both in the 4 organs, and in the 3 different age groups. We define "relative repair" as the relationship between the specific activity of DNA decomposition products and the specific activity of DNA in an irradiated test group, as compared with an unirradiated control group. In all age groups the course was similar in the liver and the spleen, especially in the young rats, as well as in the heart and the kidney. Age differences were seen to be significant in all 4 organs at particular intervals after the irradiation, which means that the maximum relative repair occurs at different times. The integration over the whole course of the investigation shows a distinct reduction in the relative repair with increasing age in all the investigated organs except the spleen, where we could not see a difference between the 2 older groups.
Stress-strain diagrams of standardizised longitudinal and transversal stripes of the thoracic aorta of 125 male Sprague-Dawley rats aged 9, 15, 24 and 30 months were recorded by an electromechanical instrument. The stripes were subjected to three successive extension-relaxation cycles. The relaxation curves of the third cycle were approximated to the functions y = a + bx and y = cxd (longitudinal stripes) and y = mxf and y = gxh (transversal stripes) respectively. The parameters could be interpreted as measures for structural and functional properties of elastic and collagenous fibers. The age changes of the curve parameters led to the following conclusions concerning age-dependent functional alterations of the aorta: The emphasis can be placed upon the increasing resistance counteracting the extension occuring with great stroke volumes. This may lead to the reduction of the capacity of the air chamber with great stroke volumes. These phenomena seem to be mainly caused by an increase of the pitch of the spiral of the collagenic fiber and the increase of the amount and/or the stability of the collagen. Age-related alterations of the elastin and of the net structure formed by the fibers influence also the distensibility at smaller extensions but seem to be less important. Therefore, the structural alterations of the aorta with age will affect the function in the first place at large stroke volumes and not be very obvious at a basic heart performance.
The motor activity as an behavioural parameter provides information about the functional state of the organism as a whole. Therefore it is an important age parameter. The results of activity measurements, however, depend strongly on the method of registration. Using 3 groups of male Sprague-Dawley rats aged 9, 15 and 29 months two methods have been tested: 1) An electronic recording: the rats were registrated in their normal cages on the Animex-Activity-Meter during the dark-phase in complete darkness. The activity measured by this method has been regarded as spontaneous activity. 2) A kinematographic method: the rats were registrated in a changed environment at constant light during the dark-phase. The activity assessed by this method has been regarded as reactive activity. Spontaneous and reactive activity show a different age dependence. For the use of the motor activity as an age parameter, both, spontaneous and reactive activity, should be assessed to get a better information about the ageing of the different functional levels of the systems governing the animal's behaviour.
Using 136 male Sprague-Dawley rats of various ages, the ageing functions of parameters originating from different organisation levels of the organism were determined. The parameters which were investigated on different levels show a non linear time dependence which can be approximated by simple or composed exponential decay-functions or by rising logarithmic functions. The results suggest a logarithmic relation between biological and chronological age.