The terminal innervation patterns in young and old guinea pig heart valves: a quantitative analysis using acetylcholinesterase staining.

The objective of this study was to determine whether and to what extent age-related changes occur in atrioventricular (AV) heart valve innervation. The AV valves from three young adult (3 months) and three older (> 24 months) female guinea pigs were studied. An acetylcholinesterase (AChE) localization method was used to prepare valve whole mounts for analysis. Two methods were used to assess nerve fiber density. Segments of the valves were drawn using a camera lucida/Nikon optiophot system. The density of nerve fibers was calculated from digitized images. The density of nerve fibers was also calculated by counting the points at which the nerve plexus intersected with the grid lines of an ocular graticule. In the bicuspid and tricuspid valves of the older guinea pigs, we observed a marked diminution in the densities of the nerve plexus, particularly in the basal zone, towards the free edges of the valve cusps, and in the chordae tendineae. Whole mount preparations such as those used in our morphological studies of the AV innervation may assist in elucidating the changes in other autonomic nerve plexuses with aging. Further work is required to establish whether and to what extent the loss of valve innervation influences the effectiveness of closure of the valves.

Contribution of cranial nerve ganglia to innervation of the walls of the rat external acoustic meatus.

The retrograde neuronal tracer, fluorogold, was used to determine the relative contributions of neurons in selected cranial nerve ganglia to the somatosensory innervation of the external acoustic meatus in the rat. Frozen sections from the trigeminal (semilunar), facial (geniculate), glossopharyngeal (superior petrosal) and vagal (jugular) nerve ganglia were examined by epifluoresence microscopy 10 to 14 days after application of the tracer dye fluorogold to the superior, inferior, anterior and posterior walls of the external acoustic meatus. The anterior wall of the canal makes a large contribution to the trigeminal ganglion and a lesser contribution to the other 3 ganglia. The trigeminal ganglion is also a major recipient from the posterior wall with smaller contributions from that wall to the geniculate and vagal ganglia. The superior wall projects a relatively constant supply to all 4 ganglia while the inferior wall primarily relays to the trigeminal and geniculate ganglia sending smaller contributions to the vagal and glossopharyngeal ganglia. In conclusion, neurons in these 4 cranial nerve ganglia contribute an overlapping supply to the 4 walls of the external ear meatus, and there is no evidence of a preferential distribution of nerve supply from one particular ganglion or nerve to specific walls of the external acoustic meatus.

Microappendages on the atrioventricular valves of the guinea pig.

More microappendages are present on both surfaces of the guinea pig tricuspid valve than on the mitral valve. The distal edge of all valve surfaces has more microappendages than the remainder of the valve surface. These results suggest that microappendage number may be the result of haemodynamic forces on the valve surface: the greater the force the smaller the number of microappendages. The function of microappendages on the surfaces of the heart valves is unknown, but two important roles have been suggested, namely to increase the surface area of the endothelial cells and to participate in the metabolism of these cells.

Innervation of the rat external auditory meatus: a retrograde tracing study.

The innervation of the rat external auditory meatus has contributions from several nerves. Fluoro-gold, a retrograde neuronal tracer, was used to determine the relative contributions from neurons in cranial and spinal ganglia, and to distinguish any difference in the sensory and motor innervation between the outer cartilaginous and inner bony portions. The following ganglia were examined: the trigeminal, geniculate, glossopharyngeal, vagal, superior cervical, and dorsal root (C2-C4) ganglia. All selected ganglia demonstrated innervation of the external ear canal, particularly the trigeminal, glossopharyngeal, facial, and vagal ganglia. The geniculate and glossopharyngeal ganglia contributed more innervation to the inner osseous portion than to the outer cartilaginous portion of the external ear canal, and the vagal ganglion contributed relatively equally.

Distribution of PGP 9.5, TH, NPY, SP and CGRP immunoreactive nerves in the rat and guinea pig atrioventricular valves and chordae tendineae.

The distribution of nerves immunoreactive to protein gene product 9.5 (PGP 9.5), tyrosine hydroxylase (TH), neuropeptide Y (NPY), substance P (SP) and calcitonin gene related peptide (CGRP) antisera was investigated in the atrioventricular valves of the Sprague-Dawley rat and the Dunkin-Hartley guinea pig using confocal and epifluoresence microscopy. No major differences were noted between the innervation of the mitral and tricuspid valves in either species. For all antisera the staining was more extensive in the guinea pig valves. Two distinct nerve plexuses separated by a 'nearly nerve free' zone were identified in both species with each antiserum tested. This was most apparent on the anterior cusp of the mitral valve. The major nerve plexus extends from the atrioventricular ring through the basal, intermediate and distal zones of the valves towards the free edge of the valve cusp. These nerve bundles, arranged as primary, secondary and tertiary components, ramify to the free edge of the valve and extend to the attachment of the chordae. They do not contribute to the innervation of the chordae tendineae. The second, minor chordal plexus, runs from the papillary muscles through the chordae tendineae and passes parallel to the free edge of the cusp. The nerves of this minor plexus are interchordal, branching to terminate mainly in the distal zone, free edge of the valve cusp and adjacent chordae tendineae. Some interchordal nerve fibres loop from a papillary muscle up through a chorda, along the free edge and pass down an adjacent chorda into another papillary muscle. The nerve fibres of the major and minor plexuses intermingle although no evidence was found for interconnectivity between them. In the distal zone between the major plexus which extends from the base of the valve and the minor chordal plexus there is a zone completely free of nerves staining with antisera to TH and NPY. Occasional nerves which stained positive for PGP 9.5, SP and CGRP immunoreactivities crossed this 'nearly nerve free zone' passing either from the chordal/free edge nerves to the intermediate and basal zones or vice versa. An additional small nerve plexus which displayed immunoreactivity to CGRP antiserum extended from the atrioventricular ring into the basal zone of the valve cusp. Not all chordae tendineae displayed immunoreactive nerve fibres. It is concluded that the innervation patterns of the sensory and sympathetic neurotransmitters and neuropeptides examined in the atrioventricular valves of the rat and guinea pig are ubiquitous in nature. The complexity of the terminal innervation network of the mammalian atrioventricular valves and chordae tendineae may contribute to the complex functioning of these valves in the cardiac cycle.

One-third, two-thirds: relationship of the radial nerve to the lateral intermuscular septum in the arm.

The radial nerve penetrates the lateral intermuscular septum of the arm before dividing into deep and superficial branches. It may be encountered in both anterior and posterior approaches to the humerus. An ability to accurately predict the point at which the nerve pierces the septum would be valuable during surgery in the arm, and would facilitate planning an approach to exploring the radial nerve after fractures of the distal humeral shaft. It would, in particular, make minimally invasive surgical techniques less dangerous. We dissected 20 cadaver upper limbs to establish whether the radial nerve enters the anterior compartment of the arm at a predictable level. We found that in almost every case the radial nerve entered the anterior compartment at a point within 5 mm of the junction of the distal and middle thirds of a line joining the lateral epicondyle of the humerus to the most lateral point of the acromion process of the scapula. This has not previously been described, and we believe is a useful aide-de-memoir to predicting the level at which the radial nerve penetrates the lateral intermuscular septum.

True aneurysm of the left ventricle: a case report and literature review.

Pathologic specimens acquired by anatomy departments may be of fundamental anatomical and clinical interest. In this report we describe a true aneurysm of the left ventricle and we review the relevant clinical records of the patient. A detailed review of the literature on ventricular aneurysms is presented with emphasis on particular aspects of cardiac anatomy.

Innervation of the rat tympanic membrane from the superior cervical and glossopharyngeal ganglia.

True Blue and Fluorogold were applied to the external surface of the tympanic membrane and middle ear mucosa of Sprague-Dawley rats and neurons in the superior cervical and glossopharyngeal ganglia were labelled with these retrograde tracer dyes. Dye absorption was poor from the tympanic membrane unless the keratinized layer was damaged with crystalline silver nitrate prior to dye application. Stained neurons were scattered throughout the superior cervical ganglion with no evidence of somatotopy. Several neurons in the glossopharyngeal ganglion stained with both dyes when these had been simultaneously applied to both sites in single animals. There was no evidence of dual staining of neurons in the superior cervical ganglion.