Robert Mayr

Internal structure of cat extraocular muscle

SummaryTeasing preparations of cat extraocular muscles (EOM) were used to study the arrangement of muscle fibers and the distribution of the different cholinesterase-positive sites, i.e. (1) large motor endplates, (2) small motor endings of the “en grappe” type, (3) myotendinous junctions and (4) myomyous junctions. The distribution of these cholinesterase-positive structures gives clear evidence of a complex muscle architecture of cat EOM. In the global layer of cat EOM, only multiply innervated muscle fibers run the whole length of the muscle. The focally innervated muscle fibers are generally shorter; they are usually arranged in series of two to three fibers being interconnected by myomyous junctions. Moreover, muscle fiber splitting is frequently present resulting in a netlike arrangement of muscle fibers. Most of the myomyous junctions occur between focally innervated muscle fibers, but also end-to-side connections of focally to multiply innervated muscle fibers are observed; multiply innervated muscle fibers have not been found connected to each other. In this layer, large motor endplates are distributed in several bands between origin and insertion. In the orbital layer all muscle fibers run from tendon to tendon, focally as well as multiply innervated ones. Here, large motor endplates are confined to a band in the middle of the muscle, and myomyous junctions are generally absent.Some functional implications of this complex architecture of cat EOM are discussed.

Course of denervation atrophy in type I and type II fibres of rat extensor digitorum longus muscle

SummaryIn the denervated extensor digitorum longus muscle of the rat type I and type II muscle fibres were differentiated histochemically and their course of atrophy was studied. Until 42 days after denervation type I and type II fibres could be identified by means of the myofibrillar ATPase reaction. Up to that time an exclusive atrophy of type II fibres was found. Type I fibres, the smallest of the normal muscle, did not change their diameters and therefore represented the largest fibres 42 days after denervation. Type II fibres of the “white” muscle portion, in which the larger IIB fibres are predominant, showed a higher rate of atrophy than those of the “red” muscle portion, in which the smaller IIA fibres are predominant: by 42 days the diameters of all type II fibres had gone down to equal values. Combined with a further progress of atrophy at later stages, there was a dedifferentiation of the histochemical properties, and the type I fibres exhibited atrophy as well. 120 days after denervation all muscle fibres were found to be highly atrophied.

Carbocyanine Postmortem Neuronal Tracing: Influence of Different Parameters on Tracing Distance and Combination with Immunocytochemistry

SUMMARY Carbocyanines (DiI, DiA, DiO) are able to travel along membranes by diffusion and therefore have been used as postmortem neuronal tracers in aldehyde-fixed tissues. Surprisingly, detailed data on the influence of different parameters on tracing distances are still missing. This study was carried out to optimize tracing procedures and to reveal the validity of the combination of postmortem tracing with immunocytochemistry. Carbocyanine crystals were applied to the cervical spinal cord, sciatic nerves, and brachial plexuses of humans and guinea pigs. Incubation in the dark at 37C for 12-15 weeks proved optimal to achieve longest tracing distances (28.9 ± 2.2 mm) in human and animal tissues. Longer incubation times and incubation temperatures higher than 37C did not result in longer tracing distances. No differences were evident between adult and newborn animals and between central and peripheral nervous system. The diffusion coefficient for DiI was calculated to be 2.5 × 10-7 cm2sec-1. After application of DiI to nerves of guinea pig extraocular muscles, DiI-positive afferent perikarya were observed in the anteromedial part of the trigeminal ganglion. These perikarya were identified by calcitonin gene-related peptide immunoreactivity (CGRP-IR). The percentage of CGRP-IR neurons after tracing was concordant with the percentage of CGRP-IR in trigeminal ganglia exclusively processed for CGRP-IR without previous postmortem tracing. These results demonstrate carbocyanines to be specific tracers for exact neuronal mapping studies.

Two fibromuscular transverse ligaments related to the levator palpebrae superioris: Whitnall's ligament and an intermuscular transverse ligament.

This study was performed to reinvestigate the detailed anatomy of the connective tissues related to the levator palpebrae superioris (LPS).

Presence and structure of innervated myotendinous cylinders in sheep extraocular muscle

Innervated myotendinous cylinders (IMCs) were for the first time described in a sheep extraocular muscle (EOMs). They were found at the distal myotendinous junction of a medial rectus and were investigated by light and transmission electron microscopy. The IMCs are enveloped by a multi-layered capsule of fibrocytes and each contains the terminal portion of one multiply-innervated muscle fibre and its corresponding tendon. The tendinous compartment of the IMC is entered by a single nerve fibre which, inside, spreads into several terminal branches. Numerous terminal branches were found among the collagen fibrils but few on the muscle fibre tips. Nerve terminals contain mitochondria and are full of clear vesicles. Within the nerve terminals, vesicles are often concentrated in an area where the axolemma exhibits dense patches. Innervated myotendinous cylinders of sheep EOMs exhibit the same ultrastructural features as those earlier described as palisade endings or myotendinous cylinders in cat, monkey and man.

Presence and morphological variability of Golgi tendon organs in the distal portion of sheep extraocular muscle

This study was undertaken to demonstrate the presence of Golgi tendon organs (GTOs) in the distal portion of sheep extraocular muscle (EOM) and to describe the morphological variability of these receptors. Extraocular muscles of a young and an old sheep were perfusion fixed and/or immersion fixed. Tissue was prepared for light microscopy and transmission electron microscopy. Immunohistochemistry was done to demonstrate the myosin pattern of the intracapsular muscle fibers of the GTOs. All GTOs in the distal portions of the sheep EOMs were located in a distinct muscle layer which was designated in a former investigation as the so‐called peripheral patch layer. Each EOM of the young sheep contained GTOs; between four and 15 GTOs were counted in the rectus EOMs. Eight GTOs were found in the superior rectus of the old sheep. Golgi tendon organs in EOMs of the young and the old sheep did not differ in their morphology. In the young sheep the mean length of the GTOs was 447 ± 132 μm (n = 60) and their mean width 101 ± 26 μm (n = 60). In the old sheep values were 576 ± 188 μm (mean length, n = 8) and 103 ± 18 μm (mean width, n = 8). The GTOs were encapsulated by perineurial cells. In 12 GTOs, only collagen bundles were inside. In the remaining GTOs (56), intracapsular muscle fibers were present. Muscle fibers entered the proximal poles of the GTOs and either terminated inside the receptors or muscle fibers left the GTOs at their distal poles. These intracapsular muscle fibers were of the multiply‐innervated type. In the GTOs variably shaped nerve terminals were found which contained a high number of mitochondria. In two GTOs, additionally, nerve terminals with aggregates of densely packed vesicles were present. Anat Rec 258:359–368, 2000.

The origin of the vestibulo-cochlear projection in the guinea pig

Previous tracer studies have revealed the sacculus to be connected to the vestibular and cochlear nuclei in the guinea pig. Due to its own innervation pattern, an anterior and posterior part of the sacculus can be distinguished. The present study investigated whether the two parts differ concerning their fiber contribution to the vestibulo-cochlear projection. After tracing the nerve of the posterior sacculus with horseradish peroxidase (HRP), the vestibulo-cochlear fibers were clearly recognizeable and showed distinct terminal labeling within the cochlear nuclei. In contrast, no terminals were identified in the cochlear nuclei after tracing the anterior sacculus. These results may further substantiate the guinea pig vestibulo-cochlear projection as a central pathway for saccular acoustic sensation.

Observations on the number, distribution and morphological peculiarities of muscle spindles in the tensor tympani and stapedius muscle of man

Although the middle ear muscles have been described for the first time more than four hundred years ago their role in modulation and transmission of sound is not yet fully understood. Surprisingly very little is known about proprioceptors in these muscles, especially in man, although this seems to be the key to the understanding of their various functions. Therefore, the question for proprioceptive sensory organs in these muscles is still relevant. The tensor tympani and stapedius muscles of four women who had donated their bodies to our institute were taken. Complete serial sections of these muscles were made which were either impregnated with silver, stained with ferric oxide for acidic polysaccharides or incubated with antibodies against S-100 protein. Thereby four to eight (mean five) muscle spindles distributed along the whole muscle could be detected in the tensor tympani muscles. These spindles contain one to three intrafusal muscle fibres and their length ranges from 140 to 4270 microm (mean 1492.8 microm). Furthermore, in three stapedius muscles one to two (mean 1.7) muscle spindles were found. They were from 350 to 500 microm (mean 482 microm) long and contained only one intrafusal muscle fiber. Regarding the diameter of intrafusal muscle fibers in both, the tensor tympani as well as the stapedius muscle, no difference to extrafusal muscle fibers of these muscles could be detected. The structure of these spindles differs considerably from those found in skeletal muscles. The morphological findings presented strongly suggest that muscle spindles occur regularly in both middle ear muscles. The results presented herein are consistent with clinical findings obtained from electromyographic studies and may help to elucidate all functions the middle ear muscles might serve in man.

Sensory innervation of the guinea pig extraocular muscles: A 1,1′-dioctadecyl-3,3,3′3′-tetramethylindocarbocyanine perchlorate tracing and calcitonin gene-related peptide immunohistochemical study

The sensory apparatus of the extraocular muscles attains special interest because of the great variation among different species with respect to the proprioceptors. The sensory innervation of the guinea pig extraocular muscles, lacking both muscle spindles and tendon organs, was investigated with a fluorescence double‐labelling method. Primary sensory perikarya were assessed by postmortem application of 1,1′‐dioctadecyl‐3,3,3′3′‐tetramethylindocarbocyanine perchlorate (Di‐I) to the extraocular muscle nerves. Traced neurons were found in the ipsilateral ophthalmic part of the trigeminal ganglion. This is in line with findings in other species. Calcitonin gene‐related peptide (CGRP) was detected immunohistochemically within the trigeminal ganglion. No somatotopic organization was observed for CGRP‐like immunoreactive perikarya. Small (maximal diameter below 30 μm), medium (maximal diameter between 30 and 50 μm), and large (maximal diameter larger than 50 μm) trigeminal ganglion cells were found among the primary afferent perikarya from extraocular muscles. Among CGRP‐like immunoreactive cells, only small and medium cells were observed. Double‐labelling experiments indicated the CGRP content of primary afferents of the guinea pig extraocular muscles. The relationship to former morphological categories of ganglion cells is discussed. Primary afferent neurons with CGRP‐like immunoreactivity might have efferent functions and might also be involved in inflammatory processes of extraocular muscles. J. Comp. Neuol. 380:16–22, 1997.

Über die Auswirkung der Hypophysektomie auf die Zellkerngröße einiger Organe der Ratte

SummaryThe changes of cell nuclear size were studied by means of a semiautomatic measuring instrument (Zeiss TGZ 3) in 8 organs of rats 15 days after hypophysectomy. The organs of normal animals sacrificed at the beginning and at the end of the 15 day experiment were used as controls. In further animals sham-hypophysectomies were performed; and the organs of these animals were examined on the 4th and on the 15th postoperative day. By means of statistical methods (t-test, variance analysis) it could be demonstrated that in all organs of the hypophysectomized animals the diameters of the cell nuclei differ significantly from those of the control groups. According to whether the organs are directly or indirectly dependent on the pituitary gland, the diameters of the cell nuclei showed a decrease between 0.6 and 16% of their normal values. The juxtaoral organ, the function of which is still unknown, showed the most pronounced decrease (−16%) of its nuclear diameter. This fact supports the hypothesis of the authors that the juxtaoral organ belongs to the group of endocrine glands dependent on the pituitary gland.ZusammenfassungAn insgesamt acht Organen der Ratte wurde das Verhalten der Zellkerngröße nach Hypophysektomie unter Zuhilfenahme eines halbautomatischen Meßgerätes untersucht. Daneben wurden die Organe von normalen Kontrolltieren zu Beginn und zu Ende eines 15tägigen Versuchs ausgewertet. Weitere Tiere wurden scheinhypophysektomiert und die Organe dieser Tiere am 4. und 15. Tage post operationem ebenfalls untersucht. Mit Hilfe von statistischen Methoden (t-Test, Varianzanalyse) konnte eindeutig erwiesen werden, daß sich die Zellkerndurchmesser bei hypophysektomierten Tieren gegenüber denen der vier Kontrollgruppen signifikant unterscheiden. Je nach der direkten oder indirekten Abhängigkeit einzelner Organe von der Hypophyse reagierten die Zellkerndurchmesser mit einer Abnahme von 0,6 bis zu 16% (Tabelle 14). Das in seiner Funktion unbekannte Juxtaorale Organ erreichte dabei den Maximalwert von minus 16%. Aufgrund des Ausmaßes der Reaktion muß es daher der Gruppe der hypophysenabhängigen inkretorischen Drüsen zugeordnet werden.