We examined cross-sectional areas of Meissner's corpuscles to evaluate the changes in their morphology and density that occur during the aging process. Our study of 10 tissue specimens from the right index finger pulp of 10 males, showed that both the size and the number of Meissner's corpuscles decrease with age. We claim greater accuracy in our data thanks to the use of a new sectioning method, namely parallel sectioning of the skin.

In a study of Japanese adults, we found that the orbital branch (OB) passing through the superior orbital fissure frequently anastomosed with the lacrimal artery or the ophthalmic artery (12/20). However, the OB passing through the meningo-orbital foramen (mof) only associationaly anastomosed with branches of the ophthalmic artery (4/79). Furthermore, the OB in the orbit, excluding the lacrimal gland as previously reported. We examined 116 cases in which the OB passed through the mof in 129 adult Japanese cadavers (45.0% in 258 sides). The OB passing through the mof was always distributed to the periorbital region and the area that it supplied was limited to the periorbita in about half of those cases. In another half of the cases (58/116), the area supplied included the lacrimal gland.

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.

In the masticatory muscles, the development of bundles of the tendon was examined: they were composed of many collagen fibers and a few elastic fibers. In the masseter muscle, the property of the tendon differs in the distribution and size of collagen fibers and elastic fibers in comparison with those of other masticatory muscles. This difference is concerned with the kinetic force for the stress or the stretch of each tendon and muscle during jaw movement.

In the American alligator, the jaw muscles show seven bundles of tendinous structure: cranial adductor tendon, mandibular adductor tendon, lamina anterior inferior, trap-shaped lamina lateralis, lamina intramandibularis, lamina posterior, and depressor mandibular tendon (originating from the musculus depressor mandibulae, m. pseudotemporalis, m. adductor mandibulae posterior, m. adductor mandibulae externus, m. intramandibularis, m. pterygoideus anterior, and m. pterygoideus posterior). These tendinous structures are composed of many collagen fibrils and elastic fibers; however, the distributions and sizes of the fibers in these tendinous components differ in comparison with those of other masticatory muscles. The differences of these properties reflect the kinetic forces or the stretch applied to each tendon by the muscle during jaw movements in spite of the simple tendon-muscle junctions. © 1993 Wiley-Liss, Inc.

The calcification levels of the mandible and the temporal bone of human fetuses, which ranged from 12 to 32 weeks of gestation, were systematically investigated with a soft X-ray analyzer linked to an image analyzer. The profile of the condylar process (head) revealed high levels of calcification, in contrast to that in the mandibular fossa of the temporal bone. The basal portion of the condylar process and the mandibular notch exhibited moderate calcification from 12 weeks of gestation. The weight and the cross-sectional areas of the muscle and the muscle fibers in masticatory muscles (masseter, temporal, medial, and lateral pterygoid muscles) are all increased gradually during development from 12 to 32 weeks of gestation. These changes in calcification and in cross-sectional area of muscle suggest that muscle development may be related to bone calcification during formation of the mandible.

We evaluated the components of nerve fibers of the motor and sensory roots of the trigeminal nerve by morphometric analysis. Trigeminal nerves were obtained from 5 cadavers (males, aged 67-95) were stained by Masson-Goldner-Goto method and examined under the microscope using a morphometric image-analyzer. The area and perimeter of axons were larger in the motor root than in the sensory root. The size distribution of axons was wider in the motor root than in the sensory root and the distribution pattern was unimodal type. These findings suggested that nerve fibers of the human trigeminal nerve gave similar findings to those of other peripheral nerves, regarding axonal size distribution and relative size of motor and sensory nerve axons.

Light microscopic and ultrastructural observations were carried out to evaluate the cell morphology and histochemistry (calcium-ATPase activity) of developing teeth in embryonic American alligators (Alligator mississippiensis). Ca-ATPase activity was observed in the distal and lateral cell membranes, rough endoplasmic reticulum (rER), mitochondria, vacuoles, and other organelles of the ameloblast, but only in the distal cell membrane and process of the odontoblast. Enzyme activity in the ameloblasts increased gradually during development. These sites of enzyme activity are related to mineralization of the enamel layer, similar to that in mammalian tooth development. Alligator teeth are heavily mineralized like mammalian teeth; however, alligator ameloblasts have undeveloped distal processes during mineralization in contrast to mammalian ameloblasts in which Tomes' processes are found near the distal portion of ameloblasts at maturation stage. The localization of intense enzyme activity in the distal and lateral ameloblast cell membrane suggests that these regions are the site of accumulation of calcium as enamel differentiates in the developing tooth. © 1993 Wiley-Liss, Inc.