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Biomedical subjects

G L Ruskell

Publications and source records attributed to G L Ruskell.

At least 37 records · Page 2Linked to original sources
PubMed1988

Distribution and termination of trigeminal nerves to the cerebral arteries in monkeys.

Wallerian degeneration was used to study the contributions of the first and second divisions of the trigeminal nerve to cerebral arterial innervation in the cynomolgus monkey. Animals were killed by intracardiac perfusion of fixative three to seven days after left ophthalmic or maxillary neurotomy or a combination of both, using three animals for each procedure. Cerebral arteries were dissected, removed and prepared for light and electron microscopy. The anterior vessels of the circle of Willis received nerve fibres, distributed via the internal carotid artery, from the ipsilateral ophthalmic branch of the trigeminal nerve and a small maxillary contribution was also observed in some animals. The posterior vessels were supplied from the same trigeminal source but by a different route, the nerves moving onto the basilar artery bilaterally or unilaterally via the recurrent nerve of the cavernous plexus using the abducent nerve for access. From the basilar, fibres distributed to both posterior cerebral arteries. Augmentation of the vascular nerve supply apparently from branches of the vagus and/or hypoglossal nerves was noted but otherwise unexamined. Trigeminal terminals were found on all vessels of the circle of Willis and their distal branches throughout the thickness of the adventitia, often lying close to the media but never contacting smooth muscle cells. These observations are consistent with results from other studies employing neurohistochemical and tracer techniques in subprimates. Comparison of operated and control material failed to reveal any distinctive features of terminals attributable to a trigeminal source.

Animals↗
PubMed1987

Trigeminal nerve pathways to the cerebral arteries in monkeys.

Two or three or sometimes more fine intracavernous branches were traced from the ophthalmic nerve using serial section reconstruction and induced nerve degeneration. They joined the cavernous plexus and were distributed forward with autonomic nerves to the adventitia of the internal carotid artery, emerging from the sinus with the artery. A strong recurrent branch from the plexus joined the abducent nerve, passed back and left the nerve at pontine level to innervate the basilar artery and the caudal circle of Willis. The recurrent nerve was absent from one side of two animals and showed asymmetry in others. No branch issued intracranially to the plexus from the maxillary nerve, but in the pterygopalatine fossa the orbitociliary branch of the maxillary nerve gave off one or two filaments that re-entered the cranial cavity through the medial infraorbital fissure and joined the cavernous plexus. Their content augmented the ophthalmic afferent distribution. All plexus branches with trigeminal fibres also contained autonomic fibres. The results show, firstly, that the cavernous plexus consists of a mixture of sensory and autonomic nerves (sympathetic and parasympathetic) and, secondly, that afferents of the internal carotid artery and rostral circle of Willis and those to the basilar artery and caudal circle of Willis are distributed separately.

Animals↗
PubMed1985

Facial nerve distribution to the eye.

Anatomical and physiological investigations indicate that facial parasympathetic (FP) innervation to blood vessels in the eye can dilate uveal vessels and raise the intraocular pressure. There is evidence that both acetylcholine and a vasoactive intestinal polypeptide (VIP) act as neurotransmitters in this system.

Animals↗
PubMed1985

Innervation of the conjunctiva.

A parasympathetic pathway from the facial nerve to the conjunctiva was confirmed. Many conjunctival nerve fibres were degenerated following pterygopalatine ganglion lesion in cynomolgus monkeys. Nerve terminal degeneration was found mainly in the large vessel walls and adjacent to the subepithelial capillaries. AChE positive nerve fibres of undenervated tissue, probably representing the cholinergic fibres of facial nerve origin, and sympathetic nerve terminals, identified by their small granular vesicle content, were similarly disposed in vessel walls. Hence conjunctival vessels, including capillaries, have a dual autonomic innervation. Intraepithelial terminals were sparse and no evidence of a specific goblet cell innervation was found. Human perilimbal conjunctiva displayed a similar distribution of nerve fibres to cynomolgus monkeys.

Acetylcholinesterase↗
PubMed1984

Effects of VIIth (facial) nerve degeneration on vasoactive intestinal polypeptide and substance P levels in ocular and orbital tissues of the rabbit.

Levels of vasoactive intestinal polypeptide (VIP)- and substance P (SP)-like immunoreactivity were measured in ocular and orbital tissues of albino rabbits. Substantial amounts of VIP were detected in the choroid (22.6 +/- 3.6 pmol g-1), and in the lacrimal (13.6 +/- 4.4 pmol g-1) and Harderian glands (20.2 +/- 4.9 pmol g-1). Somewhat less was found in the anterior uvea (3.6 +/- 1.1 pmol g-1), retina (5.4 +/- 1.3 pmol g-1) and optic nerve head (4.1 +/- 1.1 pmol g-1). Other tissues, including conjunctiva and extraocular muscle showed very little VIP-like immunoreactivity. Seven days after diathermic damage to the region of the pterygopalatine ganglion VIP was virtually eliminated from all these tissues. SP levels were also reduced, notably in the anterior uvea, probably due to concurrent destruction of sensory fibres. Electron microscopy revealed extensive degeneration of unmyelinated axons in the short ciliary nerves and in the choroid. No changes in ocular VIP levels were detected after sympathetic denervation, although a significant rise in SP was observed in the anterior uvea. The decrease in retinal VIP, believed to be confined to the amacrine cells, is considered to be a result of post-operative lid closure, rather than of VIIth nerve degeneration. Nevertheless, with this exception, VIP in ocular and orbital tissues of the rabbit appears to be contained exclusively within parasympathetic fibres of facial nerve origin.

Animals↗
PubMed1984

Sheathing of muscle fibres at neuromuscular junctions and at extra-junctional loci in human extra-ocular muscles.

Profuse sheathing of muscle fibres was noticed by chance when studying receptors in samples of extra-ocular muscle taken from orbits of six patients after eye enucleation or in the treatment of squint. The sheaths, previously unreported in any skeletal muscle, were examined by light and electron microscopy and their incidence determined. Muscle spindle capsules were rare by comparison. Most sheaths were found in the motor end plate band enclosing single muscle fibres and consisted of perineural epithelial cell extensions at neuromuscular junctions. Their length varied from a few to 225 micrometers, partly or fully covering neuromuscular junctions, and although limited attachments to muscle fibres were seen, the sheathed zones were probably not sealed off from the neighbouring endomysium. The incidence of sheathed neuromuscular junctions in inferior oblique muscles increased with age from none at 3 years to a maximum of 41% of the total in a specimen from the eighth decade. Mean length and thickness of sheaths also increased with age. Sheaths were far less frequent outside the motor end plate band, where most were related to grape endings of Felderstruktur fibres. Others contained from one to four muscle fibres and received their sheaths from passing nerves, but neuromuscular junctions were absent. A few of these were long, extending up to 470 micrometers. Sheath formation is evidently an expression of ageing in the perineurium, perhaps as a subsidiary feature of neuromuscular junction plasticity. The risk of confusing sheathed muscle fibres with muscle spindles is discussed.

Adult↗
PubMed1984

Spiral nerve endings in human extraocular muscles terminate in motor end plates.

The long held view that spiral nerve endings in extraocular muscles are sensory, recently shown to be incorrect for monkeys, was tested in man. Muscle samples were taken from orbits of five patients after eye enucleation and prepared for light and electron microscopy. Most spiral endings terminated in the motor end plate band in several well separated clusters of boutons applied to various aspects of individual fibres, in contrast to the single group of boutons of other endings. They displayed a dapple appearance using the acetylcholinesterase technique and possessed fine structural features characteristic of motor end plates. Approximately 5% of motor end plates had spiral endings and most were sheathed by extensions from perineural epithelial cells. Hence, the spiralling of nerve fibre endings in man, as in monkeys, is a device for conveying boutons to dapple motor end plates rather than for monitoring the contraction of muscle fibres. It is suggested that muscle fibres with dapple motor end plates may be responsible for the exceptional speed of contraction of extraocular muscles.

Acetylcholinesterase↗
PubMed1983

Fibre analysis of the nerve to the inferior oblique muscle in monkeys.

The nerves to the inferior oblique muscles from both sides of four rhesus and seven cynomolgus monkeys were examined by light and electron microscopy. Myelinated fibres averaged slightly over 3000 in rhesus and 2000 in cynomolgus monkeys, with a bimodal distribution of diameters in both, the lower peak being 2.5-3.0 micron and the upper 7-11 micron, the large variation of the latter applying to both species. Unmyelinated fibres were less than 10% of the total. Following intracranial ophthalmic neurectomy in five monkeys, a few unmyelinated and small myelinated fibres were degenerated in the nerve to the inferior oblique muscle (1.8% of all fibres on average). A similar proportion of fibres survived oculomotor neurectomy in three cynomolgus monkeys when the superior cervical ganglion was additionally removed. A variable number of unmyelinated fibres were degenerated in the nerve after superior cervical ganglionectomy in three cynomolgus monkeys. The experiments indicate that ophthalmic and sympathetic branches pass to the nerve to the inferior oblique muscle. The few ophthalmic nerve fibres entering the muscle appear inadequate to serve the large numbers of receptors present and therefore most of the sensory fibres probably enter the brainstem in the oculomotor nerve in both species. The sympathetic pathway to the muscle provided by its motor nerve may be augmented by others.

Animals↗
PubMed1983

Spiral nerve endings and dapple motor end plates in monkey extra-ocular muscles.

The suggestion that spiral nerve endings in extra-ocular muscles are sensory was tested. Spiral, serpentine and pincer-like endings were identified in extra-ocular muscles of rhesus and cynomolgus monkeys in light and electron microscopic preparations. Spiral and other complex nerve endings each terminated in the motor end plate zone as well separated clusters of boutons applied to various aspects of the muscle fibre, in contrast to the single group of boutons of other endings. They displayed a dappled appearance with acetylcholinesterase stain. Dapple endings had morphological features and staining characteristics consistent with motor end plates. Hence, spiralling of nerve fibre endings is shown to be a device for conveying boutons to dapple motor end plates rather than for monitoring the contraction of muscle fibres.

Animals↗
PubMed1979

The incidence and variety of Golgi tendon organs in extraocular muscles of the rhesus monkey.

Golgi tendon organs of distal tendons of rectus muscles were traced in serial transverse sections using a light microscope and their identity confirmed with an electron microscope. One or two tendon organs were present in eight of ten muscles taken from four adult rhesus monkeys and none were present in the other two. Tendon organs were unusually small averaging 270 micrometers in length and 36 micrometers in maximum width; three of them were bifid at one or both ends and the remainder were fusiform. Some lay wholly within tendon without direct attachment of muscle fibres and in the others the tip of a single felderstruktur (slow, non-twitch) muscle fibre entered the tendon organ capsule proximally and occupied the full width. Nerve terminals of most tendon organs compared with those found in other muscles with similar organelles and variety of shape. In three tendon organs with inserted muscle fibres, however, terminals with regular profiles, larger aggregations of clear vesicles and fewer mitochondria were present. The latter type of terminal and the encapsulated filderstruktur muscle fibres are features shared by the large numbers of myotendinous cylinders present in extraocular muscles and it is argued that tendon organs and myotendinous cylinders might be of common origin. If this is the case, then the overwhelming majority of myotendinous cylinders suggests that tendon organs may be an aberrant development in extraocular muscles and of little significance in the total sensory output.

Animals↗
PubMed1978

Corneal nerve access in monkeys.

Electron microscopical examination of corneal nerves in rhesus and cynomolgous monkeys revealed that limbal, subepithelial nerves gained direct access to the corneal epithelium. Epithelial axons occurred singly and infrequently and they were confined to the basal layer of cells. All nerves of the stroma terminated within the layer and rami perforans were not found. The apparent barrier to nerve passage presented by Bowman's layer in monkeys was discussed in relation to primates in general. The isolation of stromal and epithelial nerve fibres confirms that terminals occur in both layers and their respective potential for excitation was briefly discussed.

Animals↗
PubMed1978

The fine structure of innervated myotendinous cylinders in extraocular muscles of rhesus monkeys.

Many of the myelinated nerve fibres of the distal myotendinous region of rectus muscles terminate on muscle fibre tips. The terminal expansions contain aggregated, small clear vesicles and mitochondria. Neuromuscular clefts at the contacts measure 20--40 nm and are uninterrupted by a basal lamina; the sarcoplasm opposite the contacts is unmodified. Some terminals invaginate the muscle fibre tips and others contact the sides of processes formed by splitting of the tips. The muscle fibre termination, its tendon and the nerve fibre branches are encapsulated to form an end-organ averaging 125 micrometer in length and described as a myotendinous cylinder. Approximately 350 innervated myotendinous cylinders were estimated to be present in the horizontal recti with rather fewer in the vertical rectus muscles. Many of them occur shortly before the main myotendinous junction. All muscle fibres contributing to myotendinous cylinders were identified as the compact, felderstruktur, multi-innervated variety with directly apposed myofibrils that are known to be non-twitch fibres. All felderstruktur fibre terminations examined were encapsulated but 19% of them were not innervated. The nerve terminals of myotendinous cylinders are similar to those described by Dogiel (1906) as palisade endings and it is argued that they meet the morphological criteria of sensory neuromuscular endings. Their disposition suggests a capacity to monitor felderstruktur muscle fibre contraction.

Animals↗
PubMed1975

Nerve terminals and epithelial cell variety in the human lacrimal gland.

Pieces of tissue taken from three human lacrimal glands were examined electron microscopically. Secretory cells varied according to the electron density and structure of their secretion granules. Secretory cells were arbitrarily categorized as light, medium or dark based on their granule content. Acini were composed of two or all three categories of cells together with myoepithelial cells and lymphocytes. A minority ogic, sympathetic terminals. The appearance of most interstitial and all parenchymal fibres was consistent with that of cholinergic, parasympathetic terminals. Parenchymal terminals were confined to ducts, terminal tubule areas and to serous (dark) cells. A large proportion of parenchymal terminals lay adjacent to myoepithelial cells in the ducts and terminal tubule regions but terminals observed among serous cells were rarely in contact with myoepithelial cells. A possible parasympathetic control of serous secretion, granule production and duct contraction and the autonomy of mucous cells is discussed.

Axons↗