Positional Relations of the Cervical Vagus Nerve Revisited.

OBJECTIVES: The cervical part of the vagus nerve (CVN) has become an important target for stimulation therapy to treat epilepsy and psychiatric conditions. For this purpose, the CVN is visualized in the carotid sheath, assuming it to be localized dorsomedially between the carotid artery (CA) and the internal jugular vein (JV). The aim of our morphological study was therefore to revisit the CVN relationships to the CA and JV, hypothesizing it to have common variations to this classical textbook anatomy. MATERIALS AND METHODS: Positional relations of the CVN, CA and JV were investigated in the carotid sheath of 35 cadavers at the C3 to C6 level. Positional relations of the CVN, CA and JV were documented on the basis of a 3 × 3 chart. RESULTS: Eighteen different arrangements of the CVN, CA and JV were observed. The typical topographic relationship of the CVN dorsomedially between the CA and JV was only found in 42% of all cases. The CVN was located dorsally or (dorso-)laterally to the CA in 80% and dorsally or (dorso-)medially of the JV in 96% of all cases. CONCLUSIONS: Classical textbook anatomy of the CVN is only present in a minority of cases. Positional variations in contrast to textbook anatomy are considerably more frequent than previously described, which might be a hypothetical morphological explanation for the lack of efficacy or side effects of CVN stimulation. Furthermore, the position of the CVN relative to the internal jugular vein is more consistent than to the CA.

Human vagus nerve branching in the cervical region.

BACKGROUND: Vagus nerve stimulation is increasingly applied to treat epilepsy, psychiatric conditions and potentially chronic heart failure. After implanting vagus nerve electrodes to the cervical vagus nerve, side effects such as voice alterations and dyspnea or missing therapeutic effects are observed at different frequencies. Cervical vagus nerve branching might partly be responsible for these effects. However, vagus nerve branching has not yet been described in the context of vagus nerve stimulation. MATERIALS AND METHODS: Branching of the cervical vagus nerve was investigated macroscopically in 35 body donors (66 cervical sides) in the carotid sheath. After X-ray imaging for determining the vertebral levels of cervical vagus nerve branching, samples were removed to confirm histologically the nerve and to calculate cervical vagus nerve diameters and cross-sections. RESULTS: Cervical vagus nerve branching was observed in 29% of all cases (26% unilaterally, 3% bilaterally) and proven histologically in all cases. Right-sided branching (22%) was more common than left-sided branching (12%) and occurred on the level of the fourth and fifth vertebra on the left and on the level of the second to fifth vertebra on the right side. Vagus nerves without branching were significantly larger than vagus nerves with branches, concerning their diameters (4.79 mm vs. 3.78 mm) and cross-sections (7.24 mm2 vs. 5.28 mm2). DISCUSSION: Cervical vagus nerve branching is considerably more frequent than described previously. The side-dependent differences of vagus nerve branching may be linked to the asymmetric effects of the vagus nerve. Cervical vagus nerve branching should be taken into account when identifying main trunk of the vagus nerve for implanting electrodes to minimize potential side effects or lacking therapeutic benefits of vagus nerve stimulation.

Production of endogenous antibiotics in articular cartilage.

OBJECTIVE: Defensins are broad-spectrum antimicrobial peptides that are components of innate immunity. To date, only epithelial surfaces and blood cells have been shown to produce these cationic peptides in bactericidal concentrations when challenged with microorganisms or inflammatory cytokines. Infections caused by gram-negative pathogens occur only infrequently in association with joint surgery. The present study was undertaken to investigate whether this may be explained by intraarticular production of gram-negative-specialized antimicrobial peptides. METHODS: Healthy articular cartilage and cultured T/C-28a2 chondrocytes were assessed, by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry, for expression of various antimicrobial peptides. The expression of human beta-defensin 2 (HBD-2) was studied in cultured chondrocytes after exposure to bacterial supernatants and proinflammatory cytokines and was assayed by real-time RT-PCR and immunoblot analysis. A septic arthritis mouse model was used to investigate the regulation of the murine homolog of HBD-2 in articular cartilage after bacterial inoculation. RESULTS: Healthy articular cartilage and T/C-28a2 chondrocytes were able to produce different antimicrobial peptides. After exposure to gram-negative bacteria and proinflammatory cytokines, expression of cartilage-derived HBD-2 strongly increased. Immunoblot analysis revealed up-regulation of the gram-negative-specialized HBD-2 in microbicidal doses. Immunohistochemistry analysis revealed induction of the murine homolog of HBD-2 in vivo after intraarticular injection of bacteria. CONCLUSION: This study demonstrated a previously unrecognized function of human chondrocytes. In addition to its biomechanical properties, articular cartilage has the ability to produce antimicrobial substances when challenged with microorganisms. The expression of HBD-2 in microbicidal doses suggests that antimicrobial peptides may contribute to host defense mechanisms in articular joints.

Endostatin/collagen XVIII--an inhibitor of angiogenesis--is expressed in cartilage and fibrocartilage.

UNLABELLED: Aim of the study was to get a deeper insight in the mechanisms regulating avascularity of cartilaginious tissues. In the center of our interest was the expression of the anti-angiogenic fragment of collagen XVIII and its potency to inhibit angiogenesis. We observed a strong endostatin/collagen XVIII production in articular and fibrocartilage and an inhibitory potency concerning the VEGF-signalling pathway. INTRODUCTION: Cartilaginous tissue is mainly avascular and shows a limited intrinsic capacity for healing. Aim of this study was to investigate the expression of the antiangiogenic peptide endostatin/collagen XVIII in cartilage and fibrocartilage. RESULTS: In fetal epiphyseal cartilage of humans high endostatin/collagen XVIII levels could be detected by ELISA whereas significantly lower levels were found in articular cartilage of adults. In the fibrocartilaginous tissue of the menisci, there was no significant difference in the endostatin/collagen XVIII concentrations between samples of fetuses and adults. But in the menisci of adults, endostatin/collagen XVIII concentrations were higher in the internal avascular two thirds of the meniscus whereas in the fetal menisci higher endostatin/collagen XVIII concentrations were found in the external third. Endostatin/collagen XVIII immunostaining of rat articular cartilage shows that endostatin/collagen XVIII downregulation starts soon after birth. In fetal cartilage and fibrocartilage of rats and humans, endostatin/collagen XVIII could be immunostained in the extracellular matrix and in the pericellular matrix of endothelial cells, fibrochondrocytes and chondrocytes. In adult cells, weak endostatin/collagen XVIII immunostaining was restricted to the pericellular matrix of fibrochondrocytes and chondrocytes. The detection of endostatin/collagen XVIII could be verified by in situ hybridization. Chondrocytes in vitro released measurable amounts of endostatin/collagen XVIII into culture supernatants. Stimulation of chondrocytes with EGF, as an example of a growth factor, or dexamethasone had no influence on endostatin/collagen XVIII expression. Endostatin inhibited VEGF-induced phosphorylation of MAPK in chondrocytes. CONCLUSIONS: The spatial and temporal expression of endostatin/collagen XVIII in cartilaginous tissue and its potency regarding inactivation of VEGF signalling suggests that this antiangiogenic factor is important not only for the development but also for the maintenance of avascular zones in cartilage and fibrocartilage. EXPERIMENTAL PROCEDURES: We analyzed the spatial and temporal expression of endostatin/collagen XVIII--an endogenous angiogenesis inhibiting factor--in cartilage and fibrocartilage of humans and rats by immunohistochemical and biochemical (ELISA) methods and by in situ hybridization. To elucidate possible factors responsible for the induction or suppression of endostatin/collagen XVIII in cartilaginous tissues, chondrocytes (cell line C28/I2) were exposed to EGF and dexamethason. To study the possible interaction of endostatin/collagen XVIII with angiogenic factors, the immortalized human chondrocytes (C28/I2) have been incubated with VEGF and the phosphorylation of the MAPK Erk 1/2 (extracellular-regulated kinases), a known signal transduction pathway for VEGF has been determined under the influence of endostatin.

VEGF expression in adult permanent thyroid cartilage: implications for lack of cartilage ossification.

Vascular endothelial growth factor (VEGF) has been shown to play an important role during endochondral bone formation in hypertrophic cartilage remodeling, ossification, and angiogenesis, but it is not expressed in normal adult articular cartilage. Thyroid cartilage undergoes only partial ossification beginning at the age of about 20. Because it never completely ossifies, we investigated a possible role of VEGF and its receptors (VEGFRs) as well as the angiogenetic inhibitor endostatin in this permanent cartilage. In analysis of cartilage samples from all specimens evaluated, VEGF121 and VEGF165 were identified as the only VEGF splice forms expressed. In addition to VEGF, VEGFR-2 (kinase domain region/fetal liver kinase 1), but not VEGFR-1 (fms-like tyrosine kinase 1), was detectable by RT-PCR in cartilage. However, VEGFR-2 expression was only detectable up to the age of 19 years. Deposition of VEGF and VEGFR was confirmed by immunohistochemistry. VEGF concentrations measured by ELISA in thyroid cartilage increased with age in males but decreased in females. Endostatin concentrations measured by ELISA in thyroid cartilage were three times lower than in articular cartilage and showed no change with age, either in females or males. VEGF was immunostained within the intra- and pericellular matrices of some but not all chondrocytes. Thus, apart from its production in hypertrophic chondrocytes of growth plates, VEGF is also produced in single chondrocytes of thyroid cartilage. The data allow us to speculate that thyroid cartilage persists in an embryological state until it has reached its final size. After reaching its final size at the end of the second decade, VEGFR-2 is downregulated and ossification starts in the posterior part of the thyroid cartilage, proceeding ventrally. Both proteins, VEGF121 and VEGF165, should contribute to this process. VEGF concentration is high and changes in an age-related and sex-specific manner. Therefore, we postulate that VEGF is at least one of the key factors that is important for the lifelong ossification in thyroid cartilage.

The cavernous body of the human efferent tear ducts contributes to regulation of tear outflow.

PURPOSE: To test the hypothesis that the surrounding vascular plexus of the lacrimal sac and the nasolacrimal duct contributes to the regulation of tear outflow. METHODS: Experiments in 30 probands aged between 15 and 37 years were performed in both nasolacrimal systems of each subject by observing with an endoscope the transit time of an applied tear drop containing fluorescein dye until its entry into the inferior meatus of the nose. Four different experiments were performed to determine the median transit time under normal conditions and the influence on transit time of a decongestant drug, a foreign body on the ocular surface, and a decongestant drug applied together with a foreign body on the ocular surface. Comparisons were made between the right and left nasolacrimal system, in males and females, eyeglass wearers and non-eyeglass wearers, and the different experiments and the results statistically analyzed. RESULTS: The tear transit time was independent of side (right or left), gender, or eyeglass wear. It showed great individual variability. Application of a decongestant drug or placement of a foreign body on the ocular surface both prolonged the dye transit time significantly. Application of a decongestant drug simultaneously with placement of a foreign body shortened the dye transit time significantly compared with the effect of the decongestant drug alone but revealed no significant difference compared with application of a foreign body alone. CONCLUSIONS: The cavernous body of the lacrimal sac and nasolacrimal duct plays an important role in the physiology of tear outflow regulation. It is subject to autonomic control and is integrated into a complex neuronal reflex feedback mechanism starting with the dense innervation of the cornea. Moreover, its function can be pharmacologically influenced.

Region-specific immunological response of the different laryngeal compartments: significance of larynx-associated lymphoid tissue.

The occurrence of primary extranodal marginal-zone B-cell lymphoma [of the mucosa-associated lymphoid tissue (MALT) type] has only been described in the supraglottic region, implying that preexistent organized lymphoid tissue is present at that site only. To date, studies have not established clearly whether organized MALT shows a site-related distribution in the larynx. The supraglottic region of the false vocal folds and the subglottis from 87 unselected cadavers with no known history of nasal, oral, pharyngeal, laryngeal, tracheal, or esophageal disease were examined for the presence of organized MALT. Organized lymphoid tissue was found with the cytomorphological and immunophenotypic features of MALT in 100% of false vocal folds of children and in more than 90% of adolescents, decreasing to 7.1% in persons in their sixth decade, whereas MALT was completely absent in the subglottis in all age groups. The results explain why primary extranodal marginal-zone B-cell lymphoma has only been described in the supraglottic region but is absent in the subglottis. Moreover, the results suggest a region-specific immunological response of the different laryngeal areas as reflected in clinical observations and animal studies. However, the impact on presence or absence of laryngeal MALT awaits clarification.

Animal model for the absorption of lipophilic substances from tear fluid by the epithelium of the nasolacrimal ducts.

PURPOSE: To compare the nasolacrimal tissues of several species to see how closely they resemble the human and to measure nasolacrimal absorption of a substance, to show that an absorption pathway exists for substances placed in the external eye, other than directly through the cornea or conjunctiva. METHODS: The nasolacrimal systems of six different vertebrates were investigated by light microscopy to find a species with a nasolacrimal system comparable to that of humans, for use in absorption experiments. In addition to primates, rabbits were revealed by histology to have a lacrimal system closely comparable to that of humans. The rabbit lacrimal system had a stratified epithelium consisting of two layers. Subepithelially, the lamina propria was composed of two strata: loose connective tissue containing elastic fibers and lymphatic cells and a rich venous plexus comparable to a cavernous body. Rabbits were therefore chosen for the absorption experiments. (3)H-cortisol was dropped into the eyes of female rabbits. After 21, 43, or 146 minutes, the rabbits were killed, the blood collected, and the nasolacrimal systems prepared and embedded for histologic examination. Serum was obtained from the clotted blood, and radioactivity was counted. Autoradiographs of sections of rabbit nasolacrimal duct were also prepared. RESULTS: Uptake of radioactivity into the serum was high and increased with time. After 21 minutes, maximum incorporation of the applied radioactivity into the blood the level was 7.1%; after 43 minutes, 12.4%; and after 146 minutes, 15.5%. Transport of radioactivity was visualized in autoradiographs of rabbit nasolacrimal systems. CONCLUSIONS: (3)H-cortisol is incorporated from the nasolacrimal ducts into the blood of rabbits. The comparable morphology of rabbits and humans suggests that absorption of cortisol would also take place in humans. Future investigations of the nasolacrimal passage are needed to understand whether absorption of normal tear fluid components in the nasolacrimal ducts is a physiological function that also plays a role in pathologic conditions such as dry eye. The similarities between rabbit and human nasolacrimal ducts support the use of the rabbit for such studies.