Histochemical properties of the biventer cervicis muscle of the chick: a relationship between multiple innervation and slow-tonic fibre types

Abstract

Chick biventer cervicis muscle fibres have been studied histochemically. Fast-twitch, focally innervated (alpha) fibres represent 70-80% of the total fibres in this muscles. Two histochemical profiles of slow-tonic multi-innervated (beta) fibres have been observed from embryonic life the adult (three-months) stage. These two slow-tonic types differ in the activity of their histochemically demonstrated myofibrillar ATPase after either acid or alkaline preincubation, and after formalin fixation. Both slow-tonic fibre types have a high oxidative metabolism and are PAS-negative. They are referred as to beta 1 and beta 2R fibre types (slow-tonic oxidative) in an expansion of Ashmore's nomenclature, and compared to avian slow-tonic sub-types that have been described in recent reports. beta 1 and beta 2 fibre types exhibit a similar pattern of innervation. Possible explanations of the origin of histochemical heterogeneity in multiple innervated fibres are discussed.

Neuromuscular Activity of Micrurus laticollaris (Squamata: Elapidae) Venom in Vitro

“…The difference in sensitivity of the chick biventer cervicis and mouse diaphragm preparations to M. laticollaris venom is a fact. The explanation must rely not only the species selectivity of animal toxins [30,31], but also on the anatomical differences between mouse diaphragm (single innervated fiber, en plaque endings) and chick biventer end-plates (multiple innervated fiber, en grape endings) [32]. Furthermore, the existence of two populations of nicotinic receptors in BC preparations is well-known [33,34], i.e ., one population that is extrajunctional and responds well to exogenous Ach, but is rapidly blocked by venom neurotoxins, and another located in the motor end-plate that responds to nerve stimulation and is less susceptible to rapid blockade by neurotoxins (possibly because of difficulties related to toxin diffusion into the synaptic cleft).…”

Histochmical properties of myofiber types in thigh muscles of the chicken.

“…Such increases in the intensity of staining of myosin ATPase after preincubation at pH 10.4-11.0 have been shown in avian pectoralis, gastrocnemius (22) and biventer cervicis muscles (23).…”

“…In the two myofiber types the reaction for myosin ATPase remains unchanged after acid or alkaline preincubation. Two types of tonic myofibers have been recently reported to exist in the biventer cervicis muscle of the chick (23). These indicate that the staining profile for myosin ATPase varies among slow tonic myofbers and that the pH sensitivity of myosin ATPase in the tonic myofibers differs from that of mammalian type I and II myofibers.…”

“…Toutant et at. (23) have shown that slow tonic /9 myofibers are divided into /9i and /92 myofibers on the basis of the pH sensitivity of myosin ATPase in the biventer cervicis muscle. The pH sensitivity of /31 myofibers resembles that of type I myofibers of the thigh muscles, whereas the /92 myofibers appear to correspond to type SS myofibers.…”

Elimination of distributed acetylcholine receptor clusters from developing fast-twitch fibres in an avian muscle

“…They are found only as a minority constituent of some fast-twitch (type II) muscles and are innervated at distributed synaptic sites (Ashmore et al, 1978;Toutant et al, 1981;Barnard et al, 1982) by terminals variously described as "en grappe' (Hess, 1961(Hess, , 1970 or small 'en plaque' endings (Barnard et al, 1982). Muscles that consist of heterogeneous mixtures of fast (type II) and slow (type I) fibres have been shown to arise during embryogenesis independently of the nerves (Butler et al, 1982;Phillips & Bennett, 1984;Phillips et al, 1986).…”