Naruhito Otsuka

Morphometric aspects of peripheral nerves in adults and the elderly

Abstract  There have been inconsistencies among reports of age‐related differences in human peripheral nerves (PNs). For such studies, normal control values are necessary. Moreover, the diversity of methods employed makes it difficult to compare results. We used the same histological procedures and methods to measure 12 PNs: 8 in the cranial nerves, 2 motor nerves in the lower limb, and 2 nerves in the autonomic system. We performed a morphometric analysis of nerve fibers and estimated the change in the total number (TN) and average transverse area (ATA) of myelinated axons from adulthood to old age. The spinal nerves demonstrated notable age‐related changes in TN and ATA. Most of the cranial nerves also demonstrated notable age‐related changes in TN and ATA. However, some nerves demonstrated no such age‐related changes and were affected more by other factors. With regards to the autonomic nerves, the lesser splanchnic nerve indicated age‐related changes in TN, but the greater splanchnic nerve indicated no age‐related changes in either TN or ATA. The autonomic nerves were affected not only by the aging process but also by the pathological changes to the peripheral tissues that they innervate.

Development and anatomy of the spinal cord

The development and anatomy of the spinal cord are described. From the end of the third gestational week, the spinal cord sustains three developmental stages: neurulation, caudal differentiation and retrogressive differentiation. The anatomy of the spinal cord is discussed from the perspective of macroscopic findings, classification, level diagnosis, cytoarchitecture and white matter structures; especially variations of the pyramidal tract, and errors in textbook descriptions of the spinocerebellar tract.

Presynaptic protein Synaptotagmin1 regulates the neuronal polarity and axon differentiation in cultured hippocampal neurons

BackgroundHippocampal neurons in the brain polarize to form multiple dendrites and one long axon. The formation of central synapses remains poorly understood. Although several of the intracellular proteins involved in the clustering of central neurotransmitter receptors and ion channels have been identified, the signals involved in pre- and postsynaptic differentiation remain elusive. Synaptotagmin1 is an abundant and important presynaptic vesicle protein that binds Ca2+ (J Biol Chem 277:7629–7632, 2002) in regulation of synaptic vesicle exocytosis at the synapse. Synapse consists of the formation of synaptic connections and requires precise coordination of Synaptotagmin1. It was reported Synaptotagmin1 plays an important roles in the formation of axonal filopodia and branches in chicken forebrain neurons (Dev Neurobiol 73:27–44, 2013). To determine if Synaptotagmin1 could have a role in formation of axon in hippocampal neurons, we investigated the effects of Synaptotagmin1 overexpression and knockdown using the shRNA on the growth and branching of the axons of primary hippocampal neurons. We showed that overexpression of Synaptotagmin1 leads to abnormal multiple axon formation in cultured rat hippocampal neurons.ResultsWe first examined the effects of Synaptotagmin1 on the numbers of axon and dendrites. We found that the overexpression of Synaptotagmin1 led to the formation of multiple axons and induced an increase in the number of endogenous postsynaptic protein Homer1c clusters in cultured hippocampal neurons. Endogenous initial segment of axon was detected with anti-sodium channel (anti-NaCh) antibody and with anti-Tau1 (J Neurosci 24: 4605–4613, 2004). The endogenous initial segment of axon was stained with anti-NaCh antibodies and with anti-Tau1 antibodies. Then the numbers of prominence dyed positive were counted as axon. We attempted to specifically knockdown the endogenous Synaptotagmin1 with small hairpin RNAs (shRNAs). To further dissect the functions of endogenous Synaptotagmin1 in neuronal polarity, we used the shRNA of Synaptotagmin1 that specifically blocks the existence of endogenous Synaptotagmin1. When the shRNA of Synaptotagmin1 was introduced to the cells, the number of axons and dendrites did not change.ConclusionsThese results indicate that the accumulation of Synaptotagmin1 may play an important role in axon/dendrite differentiation.

Sex differences in morphometric aspects of the peripheral nerves and related diseases

BACKGROUND: The elucidation of the relationship between the morphology of the peripheral nerves and the diseases would be valuable in developing new medical treatments on the assumption that characteristics of the peripheral nerves in females are different from those in males. METHODS: We used 13 kinds of the peripheral nerve. The materials were obtained from 10 Japanese female and male cadavers. We performed a morphometric analysis of nerve fibers. We estimated the total number of myelinated axons, and calculated the average transverse area and average circularity ratio of myelinated axons in the peripheral nerves. RESULTS: There was no statistically significant difference in the total number, average transverse area, or average circularity ratio of myelinated axons between the female and male specimens except for the total number of myelinated axons in the vestibular nerve and the average circularity ratio of myelinated axons in the vagus nerve. CONCLUSIONS: The lower number of myelinated axons in the female vestibular nerve may be one of the reasons why vestibular disorders have a female preponderance. Moreover, the higher average circularity ratio of myelinated axons in the male vagus nerve may be one reason why vagus nerve activity to modulate pain has a male preponderance.

Morphometric and quantitative evaluation of the gastroepiploic artery

BACKGROUND The gastroepiploic artery (GEA) has been described in various ways by anatomical texts and surgical manuals. Currently, there are no studies that have investigated the thickness and length of GEA using gross anatomical methods. In the present study, we measured the length, circumference, area, and major axis of GEA, and quantitatively evaluated the differences between right and left GEA (RGEA and LGEA), using gross anatomical and morphometric methods for the first time. MATERIALS AND METHOD Seventeen cadavers were selected. The median age of the cadavers was 82 years. We observed and evaluated GEA with naked eyes, as well as under a stereoscopic microscope. RESULTS RGEA was significantly longer than LGEA (p < 0.0001). The mean length of RGEA and LGEA were 26.51 ± 5.15 cm and 14.05 ± 3.12 cm, respectively. The mean area of RGEA, LGEA, and the anastomotic point were 3.31 ± 1.71 mm(2), 1.33 ± 1.01 mm(2), and 0.51 ± 0.28 mm(2) respectively. CONCLUSION RGEA was significantly longer and thicker than LGEA. The results also showed that in almost all of the cases RGEA and LGEA anastomosed with each other and grew thinner as they approached the middle of the greater curvature of the stomach.

Intracranial Bony Canal of the Middle Meningeal Artery - Morphological and Histological Analysis.

The middle meningeal artery (MMA) can play an important role in the surgical revascularization. However, the MMA can be easily injured if it passes through a bony canal. We investigated the morphological and histological features of the bony canal to improve surgical results. MATERIALS AND METHODS Fifty adult dry skulls were investigated. The length of the bony canal and the distance from the orbital rim to the bony canal were measured. Additionally, 28 cadaveric heads were examined histologically. RESULTS Sixty-three bony canals were found in 43 skulls. The mean length of bony canals was 9.2 mm, and the mean distance from the orbital rim was 24.0 mm. The bony canal ran mainly from the sphenoid bone (69.8%) to the parietal bone (73.0%). Histologically, both sides of the meningeal grooves gradually closed the distance, and formed the bony canal. The MMA inside the bony canal was enveloped with collagen tissues, divided into branches, and was accompanied by the vein. CONCLUSIONS The bony canal is located around the pterion and is formed during bone growth. The MMA is covered with collagen tissues inside the bony canal. It is possible to safely expose and preserve the MMA during craniotomy with careful drilling.

A View of the Therapy for Bell’s Palsy Based on Molecular Biological Analyses of Facial Muscles

OBJECTIVE Details regarding the molecular biological features of Bells palsy have not been widely reported in textbooks. We genetically analyzed facial muscles and clarified these points. MATERIALS AND METHODS We performed genetic analysis of facial muscle specimens from Japanese patients with severe (House-Brackmann facial nerve grading system V) and moderate (House-Brackmann facial nerve grading system III) dysfunction due to Bells palsy. Microarray analysis of gene expression was performed using specimens from the healthy and affected sides, and gene expression was compared. Changes in gene expression were defined as an affected side/healthy side ratio of >1.5 or <0.5. RESULTS We observed that the gene expression in Bells palsy changes with the degree of facial nerve palsy. Especially, muscle, neuron, and energy category genes tended to fluctuate with the degree of facial nerve palsy. CONCLUSION It is expected that this study will aid in the development of new treatments and diagnostic/prognostic markers based on the severity of facial nerve palsy.

Anatomical and surgical evaluation of gastroepiploic artery

OBJECTIVE Knowledge of the anatomy of the stomach and its surrounding structures is essential for lymph node dissection. This is the first gross anatomical investigation of anastomosis variations in the gastroepiploic arteries (GEA). The aim of this study is to examine the anastomosis pattern of the right and left GEA (RGEA and LGEA, respectively). METHODS Seventeen cadavers were dissected, and the anastomotic patterns of RGEA and LGEA were observed macroscopically. RESULTS The anastomotic patterns were classified into two groups. Type 1 had direct anastomosis (n = 16; 94.1%), whereas Type 2 had no anastomosis (n = 1; 5.9%). Formation of an arterial arch along the greater curvature was observed in twelve cases (70.6%), whereas four cases (23.5%) exhibited mesh-like anastomosis or narrow anastomotic branches. CONCLUSIONS Direct anastomoses were observed in almost all the cases. These results are significant, and may be useful in the classification of lymph nodes or speculation of cancer metastases.

The impact of aging on the course of the azygos vein

INTRODUCTION The human azygos vein (AV) generally runs on the right side of the vertebral column. However, a shift in its course to the middle/left side of the vertebral column, potentially as a result of aging, has been reported. The aim of this study was to understand the relationship between AV displacement and aging. MATERIALS AND METHODS Forty-seven adult cadavers were dissected. When an AV left shift was observed, long axis AV length was measured by calculating the number of vertebral bodies under the vein. We also investigated whether a crossover vein existed between AV and hemiazygos vein at the extreme left shifting point, and whether osteophytes existed along the vertebral column. RESULTS Forty-four cadavers (94%) had left-shifted AVs. A weak positive correlation between age and the length of the left shift was observed (r = 0.3061, P = 0.0364). Thirty cadavers (64%) had crossover veins at the extreme left shifting point, and 24 cadavers (51%) had osteophytes along the vertebral column. There was no significant relationship between the length of left-shifted AVs and the existence of crossover veins or osteophytes. CONCLUSION The possibility of AV displacement to the left as part of the aging process is suggested.

Morphometric aspects of the facial and skeletal muscles in fetuses.

OBJECTIVES There are few research reports providing a comparison of the muscle fiber morphometry between human fetuses and adults. Data on fetal and adult muscle fibers would be valuable in understanding muscle development and a variety of muscle diseases. This study investigated human muscle fiber growth to clarify the difference between the facial muscles and other skeletal muscles. METHODS The materials were obtained from three male fetuses (6-month-old) and 11 Japanese male cadavers aged 43-86 years (average: 71.8). Human buccinator muscles (facial muscles), masseter and biceps brachii muscles (skeletal muscles) were resected. We counted the muscle fibers and measured their transverse area. We also calculated the number of muscle fibers per mm(2) (NMF) and the average transverse area of the muscle fibers (TAMFs). RESULTS The average of the NMF of the buccinator, masseter and biceps brachii muscles in fetuses had, respectively, 19, 37, and 22 times as many fibers as those in adults. The average fetus/adult ratios of the TAMF of the buccinator, masseter and biceps brachii muscles were 4.0%, 2.4%, 4.1%, respectively. CONCLUSIONS The average NMF for all kinds of muscles decreased after birth; however, the peak in life-span or decreases with the aging process tended to vary with the kind of muscles examined. The average TAMF for all kinds of muscles enlarged after birth. We considered that the enlargement of the TAMF was connected with the emergence of fetal movements and functional demands after birth.