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Biomedical subjects

K Greven

Publications and source records attributed to K Greven.

At least 37 records · Page 2Linked to original sources
PubMed1976

Passive stress relaxation followed by active contracture in vertebrate smooth muscles (taenia coli of the guinea pig).

1. The time course of stress relaxation following stretch was investigated in the taenia coli of the guinea pig in the relaxed (Ca2+ free bath solution with D 600) and in the contracted state (depolarization by KCl or K2SO4 in excess). The mechanical tension was standardized with respect to the volume of the samples. 2. The tension obtained by a constant stretch of 2.5 mm of the 5-15 mm samples was highest after K2SO4-depolarization (K+ = 180 mval/l) and lowest in the relaxed muscles. Muscles contracted by KCl in escess (K+ = 60 mval/l) showed intermediate values. 3. The decrease of tension by stress relaxation to a nearly constant residual value is rapidly observed in contracted muscles during about 10 s. For the relaxed muscles the same changes are slower and take place in nearly 1/2 h. 4. The relations between the extent of stress relaxation (R) and its derivative in time (dR/dt) can be expressed by a hyperbolic function. Analogous behaviour was already noted in previous studies primarily on creep. 5. The different behaviour of the muscle in the different bath solutions used is discussed with respect to the mathematical relations just mentioned. 6. Long term active reactions of depolarized muscles following stretch and stress relaxation are noted.

Animals↗
PubMed1976

Creep after loading in the relaxed and contracted smooth muscle (taenia coli of the guinea pig) under various osmotic conditions.

1. Experiments to investigate the creep phenomena of the taenia coli were performed in hypotonic (207 mosm) and hypertonic (447 or 463 mosm) media, in the relaxed (Ca2+-depletion + verapamil) as well as in the contracted (K2SO4-depolarized) state. They were compared with earlier results in isotonic media. The samples were standardized with respect to their volume (weight) before the beginning of the experiment. 2. Neither in the relaxed, nor in the contracted state was there a statistically significant difference in mean total length observed within each test series after loading with 9928 dyn for 2000 s (about 33 min) in the different osmotic media. We define total length as unloaded initial length lo + initial pure leastic extension lE + creep N. 3. In the contracted state the mean total lengths attained by elastic extension and creep are significantly greater than in the relaxed state in both hypotonic and isotonic media. The greater variance in the data for hypertonic solutions makes any statistical decision of this kind impossible. 4. The typical time course of creep (N) and particularly the hyperbolic dependance of N and dN/dt stated in an earlier paper could also be observed here under varied osmotic conditions. 5. The results suggest that the viscosity of the cell plasma is not significant for the time course and extent of creep in smooth muscles of vertebrates. Creep probably takes place in the solid structures of the cells: most particularly the contractile proteins may be involved.

Animals↗
PubMed1976

Plastic properties of vertebrate smooth muscle (taenia coli of the guinea pig).

After extension and creep due to a constant load the taenia coli of the guinea pig shows plastic deformation. The deformation is partially abolished by complete unloading: to 51% in the relaxed and to 83% in the depolarized = contracted state. The quantitative relations between creep (N) and its time derivative (dN/dt) as well as those between stress relaxation (R) and dR/dt stated in our previous papers, remain valid if plastic deformations have occurred during these processes.

Animals↗
PubMed1975

Creep after loading in relaxed and contracted (KC1 or K2SO4 depolarized) smooth muscle (taenia coli of the guinea pig).

1. The time course of creep in the taenia coli of the guinea pig was recorded during 2000 sec (33 min 20 sec) in the relaxed (Ca2+-free bath solution with verapamil) and contracted (KCl or K2SO4 depolarized) states. 2. The variations in initial length before loading (l0), immediate elastic extension after loading (lE), and creep (N) were standardized with respoect to volume (cm/cm3) and compared among the different states. 3. Immediate elastic extension (lE) and particularly creep after 2000 sec (N2000) are minimal in the relaxed and maximal in the K2SO4-contracted state. The values in the KCl-contracted state are probably affected by intracellular swelling. Statistically, there is a significant difference between the overall length (l0 + lE + N2000) in the relaxed and in the K2SO4-contracted state when creep ends. 4. The hyperbolic relation of N to dN/dt representing the time course of creep mentioned in an earlier paper is reconfirmed for the relaxed as well as for the contracted state. 5. The parameters of the equation giving this relation are calculated from the experimental data. They characterize elastic properties and inner friction during creep. It is shown that the parameters of inner friction diminish more than those characterizing the elastic properties if the preparation is changed from the relaxed into the contracted state by K2SO4-depolarization. 6. In the discussion further evidence is given that not only changes in the diameter of the preparation but also changes of the intracellular elements must be responsible for the altered time course of creep during contraction.

Animals↗