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M Skalicky

Publications and source records attributed to M Skalicky.

At least 37 records · Page 2Linked to original sources
PubMed1981

[The model in experimental gerontology (author's transl)].

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.

Aged↗
PubMed1981

[Circadian studies with young and old rats (author's transl)].

8 and 28 months old, male Sprague-Dawley rats (36 animals in each group) were used to determine the rectal temperature, various organ weights (referred to the body weight and the brain weight), various blood parameters and the concentration of Ca and Mg in the plasma and the myocard as a function of the time of the day. The values were approximated to the function y = M + A cos (omega t + phi) (y = parameter value, M = mesor, mean value of the day, A = amplitude, omega = angular velocity, t = hour of the day, phi = acrophase, when y has its highest value). The approximations were significant at 6 out of 45 parameters in both groups (rectal) temperature, pancreas weight related to the body weight, leucocyte number/mm3, GPT, Mg and Ca/Mg in the plasma). 17 parameters could be approximated only at the young rats, 1 parameter only at the old animals. In some cases large age correlated alterations of the amplitude could be observed. The mesor changed only at the pancreas weight related to the body weight. The acrophase shifted only at the leucocyte number/mm3. These variations can lead to wrong interpretations when only mean values are used for age comparisons.

Aging↗
PubMed1981

[Aspects of stress and aging in the rat (author's transl)].

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.

Aging↗
PubMed1981

[Discriminant analysis of age parameters of the rat (author's transl)].

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.

Aging↗
PubMed1981

[Problems of the assessment of biological age (author's transl)].

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.

Aging↗
PubMed1980

[Testing the effects of so-called geriatric agents].

The high average life expectation in the civilized and industrial countries can be attributed to a considerable extent to the achievements of the medical sciences. However, medical research also has the task of providing the physiological basis which will ensure that the extra years do not mean just an extension of the period of senility but instead form a period valuable for the individual and society. In accordance with the common definitions, one expects a "geriatric agent" (geriatricum) to slow down the aging process or to diminish its effects. Such influences are usually referred to as revitalization. However, a rejuvenation in the sense of a genuine reversal of the aging process is--according to our present knowledge--not possible. An objective assessment of revitalising effects can be reached by means of multivariate models of biological age, orientated on the aging process of a "normal population". However, research on human beings causes methodical difficulties and considerable expense because of the necessity for long-term studies and the importance of assessing psycho-social factors. Thus, it is necessary to test the effectiveness of "geriatric agents" primarily in the animal experiment. The laboratory rat seems well-suited for such studies. Using a multivariate model of the biological age of the rat, research into experimental influences on the aging process is demonstrated. The statistical testing and the analysis of the effects are carried out by means of discrimination analysis and factor analysis. With regard to the "geriatric agents" at present in use and the aims of experimental gerontology, it is established that such research has not yet been carried out to a satisfactory extent.

Aging↗
PubMed1979

[A mathematical model of the kinetics of collagen metabolism in the tendons and skin of young and old rats].

Two groups of 60 male Sprague-Dawley rats aged 3 and 20-24 months respectively were used to establish a 3-compartmentmodel of the kinetics of the collagen metabolism in the tail tendon and skin by means of tritium labelled L-prolin. The 3 compartments were divided into pro- and tropocollagen, labile polymer collagen and stabile polymer collagen respectively. The results suggest the following conclusions concerning the metabolism and ageing of the collagens investigated: 1. Collagen of the tendon and collagen of the skin reveal different dynamics of metabolism. 2. Stabile and labile polymeric collagen originate from different tropocollagens. 3. Both intracellular and extracellular processes are responsible for the age-changes of tendon- and skin-collagen.

Aging↗
PubMed1978

[Tensibility measurements on the rat's aorta III. Analysis of longitudinal and transversal extension as related to age (authors transl)].

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.

Age Factors↗
PubMed1978

[Time-dependent functions of the age course of age parameters of the rat (authors transl)].

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.

Aging↗