Transformation of ultrastructural type of fast-twitch muscle fibres after cross-innervation by tetrodotoxin-blocked slow muscle nerve.
ABSTRACT It is shown in rats that cross-innervation of the fast-twitch muscle extensor digitorum longus (EDL) by the nerve of the slow-twitch muscle soleus (SOL) can cause a complete transformation of the Z-band width from the fast to the slow muscle fibre type within two weeks and that it can still induce such a transformation, though usually less completely, even when impulse activity is excluded by chronical tetrodotoxin (TTX) block of the nerve. This provides a piece of clear-cut evidence for the presence of some activity-independent trophic factor in the neural determination of skeletal muscle fibre type.
- [Show abstract] [Hide abstract]
ABSTRACT: The functional integration of the smooth muscle of enterocystoplasties into the detrusor muscle was investigated in an awake-rat cystometry model and in vitro. The upper fourth of the bladder was removed, and a detubularized appendiceal segment (7 x 7 mm), with preserved vasculature, was incorporated into the bladder. After 1 or 3 months, a catheter was fixed to the top of the bladders. After a 3-day recovery, cystometries were performed. In separate experiments, agonist and nerve-induced responses were evaluated on isolated bladder strips. Cystometries revealed reduced basal pressure and micturition pressure in enterocystoplasty (ECP) bladders. Bladder capacity and micturition volume were increased. Threshold pressure (pressure immediately before micturition) was significantly lower at 1 month, but not at 3 months. Bladder compliance was significantly higher in the operated at 1 month but not at 3 months. Threshold tension did not differ between control and corresponding operated groups. Residual urine was significantly higher in the operated groups. ECP strips showed increased maximal contractions to nerve stimulation, to levels similar to those of detrusor strips. Maximal responses to carbachol increased to levels between those of intestine and detrusor. The inhibitory effect of scopolamine on nerve induced contractions increased to levels similar to those for detrusor. Purinergic activation had no effect on intestinal or ECP strips, but contracted detrusor muscle. The smooth muscle of the bowel segment in rat ECP bladders underwent a partial change in the response to nerve stimulation from that of intestine towards that of detrusor. The cystometry experiments suggested a partial functional integration of the ECP segment into the detrusor.Neurourology and Urodynamics 02/2006; 25(3):259-67. · 2.46 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The purpose of the present study was to analyse the changes of macromolecular organizations in nonjunctional sarcolemmas of different types of skeletal muscle fibres after cross-innervation. In normal rats the mean density of square arrays (6 nm particles organized in orthogonal arrays) was 9.02 / μm2 for the nonjunctional sarcolemmas of fast-twitch extensor digitorum longus (control EDL, CE) muscle fibres and 0.34 / μm2 for the nonjunctional sarcolemmas of slow-twitch soleus (control SOL, CS) muscle fibres. After cross-innervation between the fast-twitch EDL and slow-twitch SOL muscle fibres by slow and fast muscle nerves respectively for three months, the mean density was 0.45/ μm2 for the nonjunctional sarcolemmas of the operated EDL (OE) and 8.3/ μm2 for the nonjunctional sarcolemmas of the operated SOL (OS), This indicates that the cross-innervation causes a reciprocal transformation of the number and distribution of such macromolecular organizations in the electrically excitable nonjunctional sarcolemmas.Cell Research 12/1995; 5(2):143-154. · 11.98 Impact Factor