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1

Manifestations of ageing at the cytogenetic level

100%
Wojda A., Witt M.
Journal of Applied Genetics
|
2003
|
vol. 44
|
issue 3
383-399
EN
The effects of ageing in humans appear to be a combination of influence of genetically programmed phenomena and exogenous environmental factors, and take place at the cellular level (senescence), rather than at the level of the organism. There are many processes, which occur in somatic cells as a consequence of DNA replication (accumulation of DNA errors or mutations that outstrip repair processes, telomere shortening, deregulation of apoptosis, etc.) and which drive replicative senescence in human cells. DNA errors are considered to be critical primary lesions in the formation of chromosomal aberrations. It can be concluded that the chromosome aberrations are biomarkers of ageing in human cells. Studies of human metaphases, interphase nuclei and micronuclei showed the increase in loss of chromosomes and the increase in frequency of stable chromosome aberrations as a function of age.
2

Do germ-line cells in Allacma fusca (Insecta, Collembola, Symphypleona) have a higher metabolic rate than somatic cells

88%
Swiatek P., Klag J., Romek M.
Folia Biologica
|
2001
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vol. 49
|
issue 1-2
85-90
EN
Stereological analysis of the ultrastructure of primordial germ cells (PGCs) and the somatic (ectoderm) cells in two developmental stages of embryos and freshly hatched juveniles of Allacma fusca have shown great differences in mitochondria volume density (vd) between the two types of cells. In younger embryos (migration phase of the PGCs) the vd of mitochondria in the cytoplasm of the PGCs is 74.64% higher than in the ectoderm cells. In older embryos, (PGCs in the gonads) the vd of mitochondria is 123% higher than the corresponding value for the somatic cells cytoplasm. In the juvenile the vd of mitochondria in the ectoderm cells grows twice but is still only 2/3 of the value for the PGCs. On the basis of papers describing a direct relationship between stereological and physiological results the authors conclude that the metabolism of the primordial germ cells during embryonic development of Allacma fusca is much higher than that of the somatic ones. If the above conclusion is correct, the results presented here confirm the ?disposable soma theory? (Kirkwood & Holliday 1979).
3
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Senescence and learning in honeybee (Apis mellifera) workers

88%
Tofilski A.
Acta Neurobiologiae Experimentalis
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2000
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vol. 60
|
issue 1
35-39
EN
Foraging by honeybee workers was investigated from the moment of the first foraging flight until death. To minimise the influence of factors other than senescence the foragers were trained to collect food from an artificial flower close to their hive. During each foraging trip the workers repeatedly visited an artificial flower, collecting one microlitre of 50% sugar solution per visit. During the first 50 flights the mean time taken to collect one portion of food decreased significantly and the number of visits to the artificial flower per flight increased significantly. During flights following the 50th flight, the mean time taken to collect one portion of food increased significantly and the number of visits to the artificial flower per flight decreased significantly. The results confirm earlier observations that the foraging behaviour of honeybee workers is not only influenced by learning, but also by the effects of senescence.
4

Time as a growth and development factor of plants not only in in vitro cultures

75%
Dubert F., Plazek A.
Biotechnologia
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2006
|
issue 4
49-63
EN
The paper deals with time as a physical (space-time coordinate with specific properties and measure methods) as well as biological concept. Biological time is running differently taking in account various organizational levels like cell, cell organelles, whole organism and, finally, population or species. Time is a factor that regulates plant ontogenesis. In many plant species, time regulates seed dormancy and plant vernalization, photoperiodism and circadian rhythms. Time sets in motion the 'biological clock' which controls physiological and biochemical processes in plant, particularly the rate of enzymatic reactions, oscillation processes (circadian or annual rhythms), as well as internal 'cell clock' deciding upon the length of cell life as well as the rate of cell ageing processes. Senescence or death of particular cells do not mean death of the whole organism. In numerous plant species, death of individual cell is even a factor determining survival of the whole plant. The plant senescence is regulated by phytohormones such as abscisic acid, cytokinins or auxins. Time gathers new meaning in in vitro cultures. It may differ with respect to stable cell suspension culture in many cases maintaining an ability for cell multiplication for many years as compared to another fast regenerating cultures. The influence of various stress factors under in vitro conditions enables the'switching on' the clock controlling the processes of cell multiplication and differentiation.
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