Suboccipital muscles in the cat neck: Morphometry and histochemistry of the rectus capitis muscle complex

The morphometry, histochemistry, and biomechanical relationships of rectus capitis muscles were examined in adult cats. This family of muscles contained six members on the dorsal, ventral, and lateral aspects of the upper cervical vertebral column. Three dorsal muscles (rectus capitis posterior major, medius, and minor) formed a layered complex spanning from C1 and C2 to the skull. Rectus capitis posterior major was composed predominantly of fast fibers, but the other two deeper muscles contained progressively higher proportions of slow fibers. One ventral muscle, rectus capitis anterior major, was architecturally complex. It originated from several cervical vertebrae and appeared to be divided into two different heads. In contrast, rectus capitis anterior minor and rectus capitis lateralis were short, parallel-fibered muscles spanning between the skull and C1. The ventral muscles all had nonuniform distributions of muscle-fiber types in which fast fibers predominated. Dorsal and ventral muscle groupings usually had cross-sectional areas of 0.5 cm² or more, reflecting a potential capacity to generate maximal tetanic force in excess of 9 N. Biomechanical analyses suggested that one muscle, rectus capitis lateralis, had its largest moment in lateral flexion, whereas the other muscles had large, posturally dependent moment arms appropriate for actions in flexion-extension. The observation that most rectus muscles have relatively large cross-sectional areas and high fast-fiber proportions suggests that the muscles may have important phasic as well as postural roles during head movement. © 1993 Wiley-Liss, Inc.     

Distribution and innervation of short, interdigitated muscle fibers in parallel-fibered muscles of the cat hindlimb

The cat hindlimb contains several long, biarticular strap muscles composed of parallel muscle fascicles that attach to short tendons. Three of these muscles--sartorius, tenuissimus, and semitendinosus--were studied by dissecting individual gold-stained fibers and determining the surface distribution of acetylcholinesterase-stained end-plate zones. In each muscle, fascicles were composed of muscle fibers that ran only part of the fascicle length and tapered to end as fine strands that interdigitated with other tapering fibers within the muscle mass. Most muscle fibers measured 2-3 cm in length. Fascicles of muscle fibers were crossed by short transverse bands of endplates (1 mm wide by 1-5 mm long) that were spaced at fairly regular intervals from the origin to the insertion of the muscle. The endplate pattern suggested that the fiber fascicles were organized into multiple longitudinal strips. In the sartorius, the temporospatial distribution of electromyographic (EMG) activity evoked by stimulating fine, longitudinal branches of the parent nerve confirmed that each strip was selectively innervated by a small subset of the motor axons. These axons appeared to distribute their endings throughout the entire length of the fascicles, providing for synchronous activation of their in-series fibers.     

Morphometry of Macaca mulatta forelimb. II. Fiber-type composition in shoulder and elbow muscles

The present study examined the fiber-type proportions of 22 muscles spanning the shoulder and/or elbow joints of three Macaca mulatta. Fibers were classified as one of three types: fast-glycolytic (FG), fast-oxidative-glycolytic (FOG), or slow-oxidative (SO). In most muscles, the FG fibers predominated, but proportions ranged from 25-67% in different muscles. SO fibers were less abundant except in a few deep, small muscles where they comprised as much as 56% of the fibers. Cross-sectional area (CSA) of the three fiber types was measured in six different muscles. FG fibers tended to be the largest, whereas SO fibers were the smallest. While fiber-type size was not always consistent between muscles, the relative size of FG fibers was generally larger than FOG and SO fibers within the same muscle. When fiber CSA was taken into consideration, FG fibers were found to comprise over 50% of the muscle's CSA in almost all muscles.     

The intrinsic myenteric innervation of the hind-gut and accessory muscles of defaecation in the cat

Summary The anatomy and intrinsic innervation of the colon, rectum, internal anal sphincter, ano-coccygeus and recto-coccygeus have been studied in the cat with cholinesterase and catecholamine-fluorescence histochemical techniques. A variable pattern of intrinsic innervation by acetylcholinesterase-positive and adrenergic nerves along the length of the large bowel is described and is related to segmental variations in motor activity. A variation in the distribution of non-specific cholinesterase within the muscle layers is also described. Adrenergic nerves in proximal colon are arranged in the usual peri-ganglionic manner but there is also a rich direct adrenergic innervation of the longitudinal muscle in distal colon and rectum, and of circular muscle in lower rectum and internal anal sphincter. This distribution has not been reported in other species. Direct adrenergic innervation of muscle cells has been confirmed at ultrastructural level after treatment with 5-hydroxydopamine. Adrenergic neurones have not been detected in cat bowel. The ano- and recto-coccygeus muscles and internal anal sphincter possess a dense innervation of adrenergic and cholinesterase-positive nerves. It is suggested that the variation in intrinsic innervation along the large bowel should be considered in the interpretation of pharmacological and physiological experiments on this part of the gut.This work was supported by a grant from the King's College Hospital Voluntary Research Trust. We wish to thank Dr. J. P. Tranzer and F. Hoffman-La Roche & Co. Ltd., Basle, for the gift of 5-hydroxydopamine.We also thank Miss M. K. Egan and Mr. K. J. Davies for their technical assistance.     

Vasomotor innervation in the hind limb muscles of the normal and 6-hydroxydopamine treated cat

Summary Vasomotor nervous distribution to arteries in the cat gastrocnemius and soleus muscles was investigated in the normal and 6-hydroxydopamine treated animal. Muscle samples were processed for the demonstration of acetylcholinesterase by a thiocholine method and for the presence of catecholamines by a formol fluorescence technique. In isolated perfused muscle preparations noradrenaline or adrenaline increased perfusion pressure while acetylcholine or isoprenaline decreased this pressure. A beaded fluorescent periarterial plexus (not visualised after reserpine treatment) was observed. Vasomotor axons, all of which were ACHE-negative, exhibited degenerative changes following 6-hydroxydopamine injection, while ACHE-positive axons outside the adventitial sheath were unaffected. No indication of cholinergic periarterial nerves was found and our evidence suggests that the vasomotor innervation is adrenergic sympathetic in nature.This work was supported by a grant from the Medical Research Council. During the tenure of a Wellcome Trust Fellowship, Dr. F. Joó is on leave of absence from Jozsef Attila University, Szeged, Hungary. The electron microscope is on permanent loan to one of us (J. D. L.) from the Wellcome Trust. We are most grateful to Mrs. G. Howells and Miss D. Morgan for technical assistance and to Mr. P. Hire for photographic help.     

Histology, immunocytology, histochemistry and muscle fiber innervation of the pectoralis major and supracoracoideus muscles of Excalfactoria chinensis chinensis (L.)]

The morphology of the pectoralis major muscle and its antagonist, the supracoracoideus muscle, of the Chinese quail was studied in comparison with the Japanese quail, in relation to behavioral characteristics. The actomyosin ATPase reaction after alkaline and acid preincubation reveals two fibre types. The indirect immunofluorescence, using specific antibodies against 'slow' (twitch) myosin from the human vastus lateralis muscle, provokes a weak reaction. All fibres observed show focal, monoaxonal 'en plaques' endings, typical of the phasic motor system. For the two quail species, the muscle structure seems adequate in relation to the movement characteristics, meaning muscle activity of migratories, flying long distances.     

Fusimotor innervation in the cat

The motor innervation of cat spindles was examined in hindlimb muscles using a variety of techniques employed in light and electron microscopy. Observations were made on teased, silver preparations of 267 spindles sampled from the peroneal, flexor hallucis longus, and soleus muscles, hereafter referred to as the PER/FHL/SOL series. The γ innervation. Trail endings are almost invariably present, and innervate both bag and chain muscle fibres. Trail fibres accounted for 64.6 to 74.8% of the total fusimotor supply to samples of spindle poles in the PER/FHL/SOL series, the mean number of fibres per pole varying from 2.7 to 5.0 in the different muscles, and the mean number of ramifications (areas of synaptic contact) per fibre being 3.7. By contrast, the p?innervation of a spindle pole generally consists of a single fibre supplying only one plate. In the above samples p(2) fibres accounted for 4.1 to 28.0% of the total fusimotor supply, and the mean number of fibres per pole varied from 0.3 to 1.2 in the different muscles. Ninety per cent of p(2) plates innervate bag fibres. The α innervation. The structure of p?plates as seen in both light and electron microscopy compares very closely with that of extrafusal plates. After nerve section p?plates degenerate at the same time as extrafusal plates, being the first of the three types of fusimotor ending to disappear. The frequency of the p?innervation is similar to that of the p?innervation. In the same samples of PER/FHL/SOL spindle poles as above p? fibres accounted for 6.0 to 28.8% of the total fusimotor supply, the mean number of fibres per pole varying from 0.25 to 2.1 in the different muscles. The majority of p? fibres enter a pole to terminate in one plate only. Seventy-five per cent of the plates innervate bag fibres. The three types of fusimotor ending are thus not selectively distributed to the two types of intrafusal muscle fibre. All three types of fusimotor fibre may branch within the spindle so as to innervate both bag and chain fibres. Bag fibres receive both types of plate ending as well as trail endings. Most chain fibres receive trail endings only; the rest receive either a p?or a p?plate innervation in addition, 25% of the p?and 10% of the p?innervation being distributed to chain fibres. The significance of this nonselective innervation is interpreted as indicating that the type of contraction elicited by stimulating a fusimotor fibre depends upon the type of ending initiating it rather than upon the type of muscle fibre executing it. Reasons are given for concluding that the dynamic response is controlled via the p?and p?plates, and that the static response is controlled by the trail endings. The participation of the α fibres in mammalian fusimotor innervation, previously regarded as a vestigial feature, proved to be widespread in the muscles studied and more prevalent in fast muscles (FHL, peroneus digiti quinti) than slow (soleus). A low frequency of p?innervation is offset by a high frequency of p?(as in peroneus longus), and vice versa (as in FHL). It is unlikely that collaterals from slow α fibres innervating type B muscle fibres are wholly responsible for the high frequency of the p?innervation in FHL, and it is suggested that collaterals may also be derived from fast α fibres innervating type C muscle fibres. The possibility of there being some motor fibres of α conduction velocity and with an exclusively fusimotor distribution is also taken into account.     

Significance of the pattern of motor innervation of the intrinsic laryngeal muscles of cat.

Simple and compound forms of motor endings, showing a particular distribution, were found in the intrinsic laryngeal muscles of the cat. The muscles carrying compound and multiple endings were stained densely black with Sudan black B; while the muscles with simple and single endings showed black and pale fibres. A probable relationship is suggested between the contraction properties and the pattern of motor innervation of intrinsic laryngeal muscles of the cat.     

Anatomy and histochemistry of spread-wing posture in birds. 3. Immunohistochemistry of flight muscles and the "shoulder lock" in albatrosses

As a postural behavior, gliding and soaring flight in birds requires less energy than flapping flight. Slow tonic and slow twitch muscle fibers are specialized for sustained contraction with high fatigue resistance and are typically found in muscles associated with posture. Albatrosses are the elite of avian gliders; as such, we wanted to learn how their musculoskeletal system enables them to maintain spread-wing posture for prolonged gliding bouts. We used dissection and immunohistochemistry to evaluate muscle function for gliding flight in Laysan and Black-footed albatrosses. Albatrosses possess a locking mechanism at the shoulder composed of a tendinous sheet that extends from origin to insertion throughout the length of the deep layer of the pectoralis muscle. This fascial "strut" passively maintains horizontal wing orientation during gliding and soaring flight. A number of muscles, which likely facilitate gliding posture, are composed exclusively of slow fibers. These include Mm. coracobrachialis cranialis, extensor metacarpi radialis dorsalis, and deep pectoralis. In addition, a number of other muscles, including triceps scapularis, triceps humeralis, supracoracoideus, and extensor metacarpi radialis ventralis, were found to have populations of slow fibers. We believe that this extensive suite of uniformly slow muscles is associated with sustained gliding and is unique to birds that glide and soar for extended periods. These findings suggest that albatrosses utilize a combination of slow muscle fibers and a rigid limiting tendon for maintaining a prolonged, gliding posture.     

Comparative histology, histochemistry and innervation of the striated muscle fibers of the peroneus longus muscle

The morphology of the peroneus longus muscle was compared in three Galliformes and five Passeriformes in relation to partial behavioral characteristics. In the quail two fibre types are found, while the muscle of the other species is composed of three fibre types. The frequencies of these fibres are different, especially between Galliformes and Passeriformes. The peroneus longus muscle in the quail is innervated only from the phasic system. The other species show phasic and tonic innervation. There is a correlation between the muscle fibre calibre and the extent of the synaptic gutter.     

Catecholaminergic innervation of muscles in the hindgut of crustaceans

Summary The crustacean species Pacifastacus leniusculus and Gammarus pulex were investigated by electron microscopy in a search for possible neuromuscular junctions in the hindgut, which has a rich supply of catecholaminergic fibres. True neuromuscular synapses were found in both species between nerve terminals containing dense-core vesicles (80–110 nm in diam.) and muscle fibres. We suggest that the dense-core vesicle terminals contain a catecholamine, and this is supported by ultrahistochemical tests for monoamines. Two types of junctions are found: one in which the nerve terminal is embedded in the muscle cell (both species) and one in which protrusions from the muscle cell meet nerve terminals (Pacifastacus). Gammarus pulex, which has only circular muscles in the hindgut, has only catecholaminergic innervation, whereas Pacifastacus leniusculus has circular and longitudinal muscles both with at least two types of innervation.The investigation was supported by grants from the Swedish Natural Science Research Council (B 2760-009), the Hungarian Academy of Sciences, the Royal Swedish Academy of Sciences, and the Magnus Bergvall Foundation. We are also indebted to Mrs. Lena Sandell for her skilful technical assistance     

Enzyme histochemistry of the mesocoxal muscles of Periplaneta americana

Histochemical techniques have been employed to characterize enzymatic activity in the mesocoxal muscles of the cockroach, Periplaneta americana. Through our studies of the enzymes myosin-ATPase, NADH reductase, succinic dehydrogenase (SDH), and lactic dehydrogenase (LDH), we were able to classify fibers within these muscles according to criteria established for muscle fibers of vertebrates. Many of the mesocoxal muscles possess two different and distinct populations of fibers, whereas the remaining muscles are homogeneous with respect to their constituent fibers. The data presented here indicate biochemical heterogeneity for muscles of differing structural and functional features and possible neurotrophic influences upon oxidative enzymes and myosin-ATPase isozymes.