Identification of abducens motoneurons, accessory abducens motoneurons, and abducens internuclear neurons in the chick by retrograde transport of horseradish peroxidase.

The location of the motoneurons innervating the lateral rectus, pyramidalis, and quadratus muscles of the chick has been determined by application of horseradish peroxidase (HRP) to these muscles and their nerve branches, and internuclear neurons in the abducens nucleus have been identified by injection of HRP into the oculomotor nucleus. Quantitative results were obtained by means of a semiautomatic image analyzer. Lateral rectus motoneurons were observed only in the ipsilateral principal abducens nucleus, where they numbered 500-550, and quadratus and pyramidalis motoneurons only in the ipsilateral accessory abducens nucleus. The 325-375 internuclear neurons that appeared in the principal abducens nucleus contralateral to the oculomotor nucleus injected with HRP were practically confined to the rostral two thirds of the nucleus, where they tended to surround the lateral rectus motoneurons in dorsal or lateral positions, though a minority of interneurons also mingled with the motoneurons in the center or at the medial face of the nucleus. Most interneurons were small and elongated, but a minority of larger interneurons morphologically similar to the lateral rectus motoneurons were also distinguishable. The 100-110 quadratus motoneurons and the 45-55 pyramidalis motoneurons mingled in the accessory abducens nucleus were larger than the lateral rectus motoneurons and sent their axons into the ipsilateral abducens nerve.

The postganglionic parasympathetic fibers originating in the otic ganglion are distributed in several branches of the trigeminal mandibular nerve: an HRP study in the guinea pig.

Application of HRP to the proximal stumps of the ramifications of the trigeminal nerve shows that all those belonging to the mandibular branch contain parasympathetic fibers originating in the otic ganglion. The nerve with the largest proportion of these fibers is the auriculotemporal nerve (50-60% of all labeled neurons), while the smallest percentages are found in the lingual nerve and motor root (about 5% each). The presence of otic fibers in the inferior alveolar, mylohyoid, buccal and motor branches of the trigeminal nerve has not hitherto been reported.

Quantitative histochemical study of changes with age in intracellular lipids of xiphisternal cartilage in rat and rabbit.

Histological and histochemical methods have been employed to study the histology and intracellular lipid distribution of xiphisternal cartilage in rats and rabbits of 5 different ages ranging from newborns to old adults. Xiphisternal cartilage was subdivided for the purposes of the study in 12 regions, and observations were quantified using an image analyser. Large differences in intracellular lipid distribution were observed among different cell populations of individual regions, among different regions of individual cartilages, and among cartilages from animals of different ages. The 2 species studied also differed widely as regards the distribution and quantity of intracellular lipids, even with respect to regions of similar histological characteristics occupying the same relative position within the cartilage. In particular, in the rat the chondrocytes of the lateral edges an the distal third are those possessing the greatest amounts of triglycerides whereas in rabbit these regions are the least rich in triglycerides.

Quantitative morphological and histochemical study of the xiphisternal cartilage and its intracellular lipids in the guinea-pig.

The xiphisternal cartilages of newborn, suckling, immature and adult guinea-pigs were divided into twelve regions in a study of their histology and intracellular lipid content. Histochemical methods were employed, and the observations quantified using a semi-automatic image analyser. In general, triglyceride content increases with age and is lower in surface layers and in distal and lateral regions than in deep layers and proximal and medial regions. Phospholipids, on the other hand, diminish with age and are most abundant in surface layers and in distal and lateral regions. The nature and quantity of these lipids in the various regions and layers into which the cartilages were subdivided has been related to the size of the lacunae in which the cells lie.

Localisation of motoneurons supplying the extra-ocular muscles of the rat using horseradish peroxidase and fluorescent double labelling.

This paper describes a qualitative and quantitative investigation into the location of the motoneurons innervating the extra-ocular muscles of the rat. Injections of horseradish peroxidase, bisbenzimide, propidium iodide and DAPI-primuline were made either in one or simultaneously in two muscles. Unlike those of the cat, rabbit and monkey, the motoneurons which make up the oculomotor nucleus of the rat are not arranged in spatially separate subgroups belonging each to its corresponding extra-ocular muscle, but instead allow a high degree of superposition among the motor pools which they compose. The motoneurons innervating the lateral rectus and inferior oblique muscles are all homolateral; those of the medial and inferior rectus muscles are mainly homolateral with a few contralateral exceptions; and those of the superior rectus, levator palpebrae and superior oblique muscles are mainly contralateral with a small minority of homolateral exceptions. As well as from the main motor pools with which they are associated, the medial rectus, inferior rectus, superior rectus, levator palpebrae, superior oblique and lateral rectus muscles all receive innervation from motoneurons lying among the fibres of the fasciculus longitudinalis medialis. All these observations are supported by quantitative data.