Human Frontalis Muscle Innervation and Morphology.

Due to its clinical importance and due to a suggestion regarding the afferent innervation, the microscopic appearance of the frontalis muscle was investigated. Methods: From seven human cadavers, serial sections of the frontalis muscle were studied using light microscopy. Immunhistochemistry was performed using antibodies against collagen XXII and neurofilament. Results: The macroscopic appearance of the muscle was in accordance with the literature. At both insertion sides, the muscle fiber endings expressed collagen XXII, a marker for myotendinous junctions, although no tendons were present at the origin side. Neuromuscular junctions were seen in the middle part of the muscle belly (insertion of the nerve fibers of the facialis nerve) and in the cranial part toward the galea aponeurotica (possible afferent fibers?). Conclusions: This study summarizes the microscopic appearance of the frontalis muscle. It is a first example that collagen XXII can be expressed even without tendon formation. It confirms the absence of corpuscular afferent neuronal structures within the muscle.

Muscle spindles in the rhesus monkey platysma.

The platysma of the rhesus monkey consists of two parts: a platysma myoides located similar to the human platysma, and a platysma cervicale passing the dorsal cervical region and being in contact with the cheek pouch. Our investigation showed that the muscle fiber morphology was comparable in both parts. Muscle spindles were only present in regions connected to the cheek pouch and contained only nuclear chain fibers. It is tempting to speculate that they sense the filling of the cheek pouch rather than mimic activities.

In the human, true myocutaneous junctions of skeletal muscle fibers are limited to the face.

Within the panniculus carnosus-associated skeletal muscles in the human, the palmaris brevis and the platysma showed myotendinous/myofascial junctions with clear distance to the corium and the specific connection collagen type XXII. The orbicularis oris muscle, in contrast, contained bundles of striated muscle fibers reaching the corium at two distinct levels: the predominant inner ending was connected to the elastic network of the inner corium and the outer ending was within the more superficial collagen network. At both locations, the striated muscle fibers showed brush-like cytoplasmic protrusions connecting a network which was not oriented toward the muscle fibers. Collagen type XXII was not present.

Characterization of afferent corpuscular sensors of the human palmaris brevis muscle.

The palmaris brevis muscle contains numerous muscle spindles to control changes of the muscle length but is devoid of tendon-associated neuronal elements (e.g. Golgi tendon organs or Ruffini-like corpuscles) controlling changes in muscle strength. Pacinian bodies, frequently seen in the palm of the hand, show no direct association to the muscle bundles. The observed innervation pattern of the palmaris brevis muscle points to a specific type of neuronal regulation, present in skeletal muscles with no skeletal connection.

The human platysma contains numerous muscle spindles.

The mimic muscles are usually described as containing no muscle spindles. In the present publication the human platysma was reinvestigated concerning its content of corpuscular sensors. Serial sections through the platysma of seven donors revealed numerous muscle spindles but no Pacini corpuscules. The muscle spindles were located in the cranial two-thirds of the platysma, and were evenly distributed with a tendency to have more spindles in the lateral part of the muscle. Immunohistochemical staining with S46 antibodies revealed a predominance of nuclear bag fibers. The results point to an extended function of the platysma as an afferent center of the lower face mimic muscles.

Axolotls with an under- or oversupply of neural crest can regulate the sizes of their dorsal root ganglia to normal levels.

How animals adjust the size of their organs is a fundamental, enduring question in biology. Here we manipulate the amount of neural crest (NC) precursors for the dorsal root ganglia (DRG) in axolotl. We produce embryos with an under- or over-supply of pre-migratory NC in order to find out if DRG can regulate their sizes during development. Axolotl embryos are perfectly suitable for this research. Firstly, they are optimal for microsurgical manipulations and tissue repair. Secondly, they possess, unlike most other vertebrates, only one neural crest string located on top of the neural tube. This condition and position enables NC cells to migrate to either side of the embryo and participate in the regulation of NC cell distribution. We show that size compensation of DRG in axolotl occurs in 2 cm juveniles after undersupply of NC (up-regulation) and in 5 cm juveniles after oversupply of NC (down-regulation). The size of DRG is likely to be regulated locally within the DRG and not via adaptations of the pre-migratory NC or during NC cell migration. Ipsi- and contralateral NC cell migration occurs both in embryos with one and two neural folds, and contralateral migration of NC is the only source for contralateral DRG formation in embryos with only one neural fold. Compensatory size increase is accompanied by an increase in cell division of a DRG precursor pool (PCNA+/SOX2-), rather than by DRG neurons or glial cells. During compensatory size decrease, increased apoptosis and reduced proliferation of DRG cells are observed.

Stress reaction in outer segments of photoreceptors after blue light irradiation.

The retina is prone to oxidative stress from many factors which are also involved in the pathogenesis of degenerative diseases. In this study, we used the application of blue light as a physiological stress factor. The aim of this study was to identify the major source of intracellular ROS that mediates blue light-induced detrimental effects on cells which may lead to cytotoxicity. We hypothesized that outer segments are the major source of blue light induced ROS generation. In photoreceptors, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) enzymes and the recently found respiratory chain complexes may represent a major source for reactive oxygen species (ROS), beside mitochondria and chromophores. Therefore, we investigated this hypothesis and analysed the exact localization of the ROS source in photoreceptors in an organotypic culture system for mouse retinas. Whole eyeball cultures were irradiated with visible blue light (405 nm) with an output power of 1 mW/cm². Blue light impingement lead to an increase of ROS production (detected by H2DCFDA in live retinal explants), which was particularly strong in the photoreceptor outer segments. Nox-2 and Nox-4 proteins are sources of ROS in blue light irradiated photoreceptors; the Nox inhibitor apocynin decreased ROS stimulated by blue light. Concomitantly, enzyme SOD-1, a member of the antioxidant defense system, indicator molecules of protein oxidation (CML) and lipid oxidation (MDA and 4-HNE) were also increased in the outer segments. Interestingly, outer segments showed a mitochondrial-like membrane potential which was demonstrated using two dyes (JC-1 and TMRE) normally exclusively associated with mitochondria. As in mitochondria, these dyes indicated a decrease of the membrane potential in hypoxic states or cell stress situations. The present study demonstrates that ROS generation and oxidative stress occurs directly in the outer segments of photoreceptors after blue light irradiation.

Comparative morphometric and immunohistological assessment of the development of restenosis after arterial injury and a cholesterol-rich diet in apolipoprotein E -/-mice and C57BL/6 control mice.

OBJECTIVE: Animal models of restenosis have been a cornerstone of testing potential therapies and have improved the understanding of the underlying mechanisms. The aim of this study was to provide an in-depth comparison of the progression of restenotic lesion formation after arterial injury in apolipoprotein E -/- and C57BL/6 control mice. METHODS: In this study, we investigated the difference in lesion formation of apolipoprotein E -/- and C57BL/6 controls on a high-cholesterol, high-fat diet after arterial injury. One week prior to arterial injury of the left femoral artery, mice were started on a high-cholesterol, high-fat diet. Diets were continued after arterial injury until euthanization. At five consecutive time points (2, 5, 10, 15, and 21 days), the intimal hyperplasia in the injured arteries was analyzed. RESULTS: In the C57BL/6 control mice, a continuously increasing lesion formation, consisting primarily of alpha-smooth muscle actin-positive cells, was observed. Lesion formation in apolipoprotein E -/- mice was significantly more pronounced, resulting in complete occlusion of the arteries in four out of five vessels after 21 days. Lesions in apolipoprotein E -/- mice consisted predominantly of lipid-loaded foam cells and alpha-smooth muscle actin-positive cells. Further histological evaluation demonstrated cholesterol crystals in the lesions and neovascularizsation in cases of occlusion. CONCLUSIONS: Thus, apoE -/- mice on a high-cholesterol, high-fat diet provide a more valid model for the characterization of the development of restenotic lesions after mechanical irritation such as angioplasty than C57BL/6 mice.

Developmental aspects of galectin-3 expression in the lens.

In order to investigate the temporal and spatial expression pattern of the lectin galectin-3 during lens development we performed immunohistochemical studies using monoclonal and polyclonal antibodies against galectin-3 on paraffin sections of human, mouse and rat eyes. Galectin-3 has been shown to be involved in various biological functions related to cell adhesion, proliferation, apoptosis and differentiation in other tissues. In the human lens, galectin-3 shows a selective expression pattern during lens development. It is present in all cells of the early lens vesicle and at later stages it is strongly expressed during the elongation phase in differentiating primary lens fibres. From about 7 weeks onwards the anterior lens epithelium fails to express galectin-3. Adult lenses, however, exhibit immunoreactivity in the anterior epithelial cells and in the early differentiating secondary fibres of the lens' outer cortex prior to the onset of degradation of the nuclei. In contrast to the observed expression pattern in prenatal human lenses, mouse and rat lenses exhibited immunoreactivity for galectin-3 during postnatal and adult stages only. At these stages, the expression pattern closely resembles that seen in the corresponding human lenses. The spatiotemporal pattern of galectin-3 distribution during lens development favours a role of this lectin in adhesion processes and in the regulation of programmed organelle elimination during lens cell differentiation.