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1

Anchorage-dependent chick embryo fibroblasts synthesise DNA and proliferate when cultured in multilayered sheets suspended among glass fibres

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Czyz J., Dobrucki J., Korohoda W.
Folia Biologica
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2001
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vol. 49
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issue 1-2
1-12
EN
Chick embryo fibroblasts (CEFs) spontaneously form multicellular and multilayered sheets suspended on the network of glass fibres which are stabilized by fibronectin containing protein deposits located at cell-to-cell contacts. The cells situated within the sheets are surrounded by the neighbouring cells and their mechanical equilibrium is stabilised by intercellular ?parabaric? effects. It was found that CEFs in the sheets retain relatively high mitotic activity corresponding to that observed in sparse monolayer cultures. These cells grew up to much higher local density than in confluent and contact-inhibited monolayer cultures and developed an abundance of microfilament bundles that terminated at vinculin-containing protein complexes. The results presented demonstrate that direct contact with solid substratum, cell-to-cell contacts, local cell density, and intercellular exchange of humoral factors are not directly involved in the density-dependent inhibition of growth observed in monolayer cultures. They also support the concepts concerning the role of mechanical equilibrium of cell membrane and sub-membranous cytoskeleton in the regulation of proliferation of non-transformed cells.
2

Spreading-independent growth of normal fibroblasts in three-dimensional cultures

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Czyz J., Rajwa B., Bzowska M., Dobrucki J., Korohoda W.
Folia Biologica
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2004
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vol. 52
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issue 1-2
19-24
EN
Changes of cell shape resulting from cellular flattening on culture substratum have previously been demonstrated to correlate with mitotic activity of normal animal cells in monolayer cultures. Here, we compared the shapes and proliferation of chick embryo fibroblasts cultured either in multicellular, multilayered sheets extended between glass fibres, or in standard monolayers. Fibroblasts in sheets retained the mitotic activity characteristic of that observed in sparse monolayer cultures, i.e. considerably higher that in confluent monolayers. Morphometric analyses revealed, however, that the cells in sheets were considerably less flattened than in monolayer cultures. These observations indicate that the modulation of culture conditions resulting in multidirectional cell stretching leads to the dissociation of flattening and mitotic activity of normal animal cells, so long as an intracellular stress field, generated by contractile cytoskeleton and stabilised by intercellular contacts, is maintained.
3
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Fatigability of motor units estimated by changes in work performed during their repetitive stimulation during the fatigue test

100%
Celichowski J., Grottel K., Bichler E.
Acta Neurobiologiae Experimentalis
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1999
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vol. 59
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issue 1
37-43
EN
In numerous studies resistance to fatigue is evaluated by measuring the peak tension of motor units in muscle. In the present study, the work performed within successive tetani during the fatigue test of rat medial gastrocnemius motor units was estimated by assessing of the area under the tension record. Resistance to fatigue was evaluated by a modified fatigue index which is expressed as the ratio of the area under a tetanus recorded two minutes after maximal potentiation of tension has been reached to the area under this maximally potentiated tetanus. The values of this modified fatigue index were compared to the standard fatigue index which was taken as the ratio of peak tensions for corresponding tetani. For fast fatigable units, values of the modified fatigue index were significantly lower than those of the standard index. This observation resulted from changes in the shape of unfused tetani accompanying developing fatigue. These changes strongly influenced the area under the tension record whereas the peak tension of these tetani diminished less significantly. For slow and a part of fast resistant to fatigue units (with the standard fatigue index above 0.85) the modified fatigue index was slightly higher than the standard one although the difference was not significant. This phenomenon was due to the prolongation of relaxation which was visible in the last part of the fatigue test. It is being concluded that the modified fatigue index describes more precisely the fatigue-induced changes in tetani during the fatigue test than the standard fatigue index, especially in fast fatigable units.
4
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The area under the record of contractile tension: estimation of work performed by a contracting motor unit

100%
Celichowski J., Grottel K., Bichler E.
Acta Neurobiologiae Experimentalis
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1998
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vol. 58
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issue 2
165-168
EN
The area under twitch tension records was measured for motor units in rat medial gastrocnemius. These measures were compared to measures of tension. The tension varied in significantly larger range than the area. The area of slow motor units was similar to the area of fast resistant units, whereas their tensions differed significantly. The area depended mainly on the amplitude of contraction and to a smaller degree on its time course. The measure of area under the tension record gives a more exact evaluation of the work performed by contracting motor units than the measure of tension alone. The obtained results show that motor units in mammalian muscle are less variable in their ability to perform contractile work and moreover, that slow motor units play a more significant role during contractions than was supposed based on tension measures.
5
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The influence of a doublet of stimuli at the beginning of the tetanus on its time course

100%
Celichowski J., Grottel K.
Acta Neurobiologiae Experimentalis
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1998
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vol. 58
|
issue 1
47-53
EN
The influence of a pair of stimuli generated in a short time sequence (doublet) at the beginning of stimulation on the time course of the following tetanus was investigated. Experiments were performed on single motor units in rat's medial gastrocnemius. The doublet evoked an increase in tetanic tension, tetanic fusion and the area under tension record. These effects were measured in tetani fused to varying degrees. It was found that for all types of motor units the strongest influence of the doublet was observed in half-fused tetani. Moreover, the doublet influenced the first part of tetanus significantly more as compared to the second. Slow motor units showed greater sensitivity of the tension and the tetanus area to the doublet than fast units. The results show that slow units are characterized by better summation of their tension at the beginning of a tetanus. a tetan
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