During development, dorsal root ganglion (DRG) neurons in higher vertebrates extend their axons centrally to the spinal cord through the dorsal root entry zone (DREZ) and peripherally to muscle and skin targets. After entering the spinal cord, DRG axons project into the dorsal mantle layer. In this review, we focus on evidence showing the role for netrin-1 in forming sensory axonal trajectories. Netrin-1 is a diffusible axonal guidance molecule that chemorepels developing DRG axons. When DRG axons project toward the DREZ, ventral spinal cord-derived netrin-1 prevents DRG axons from projecting aberrantly toward the ventral spinal cord. At later stages, the dorsal spinal cord cells transiently express netrin-1. This dorsal spinal cord-derived netrin-1 prevents DRG axons from invading the dorsal spinal cord during the waiting period. Together, the data reviewed provide strong evidence that netrin-1 plays a crucial role in sensory axon projection during development.
We assessed the usefulness of the separate demonstration of the arterialand venous phase on 3D-CT angiography (3D-CTA) using a 64-multidetector row CT (MDCT) scanner for the surgery of brain tumors. Nineteen patients with meningiomas (n=11), schwannomas, metastatic brain tumors (n=2 each), glioblastoma multiforme, malignant lymphoma, craniopharyngioma, and embryonal carcinoma (n=1 each) underwent scanning on a 64-MDCT scanner. After dynamic CT scanning to determine the scan timing for the arterialand venous-phase, we individually scanned the arterial- and venous phase for 4 sec after injecting a nonionic contrast medium. Using the CT threshold setting and subtraction and cutting techniques, we produced individual 3D-CT images of the arteries, veins, tumors, and bones. The operators subjectively assessed the usefulness of these images in comparison with 3D-CTA. We separately demonstrated the arterial- and venous phase on 3D-CTA covering the entire head in all 19 cases. The 3D-CT arteriographs, 3D-CT venographs, and the fused 3D-CT images facilitated our understanding of the 3D anatomic relationship among the tumor, arteries, veins, and bony structures. In 14 of 19 cases our method provided the surgically valuable findings ; the information on the anatomical relation between tumor and the surrounding arteries and veins (in 13 cases) the identification of anatomical course of the encased vessels (in one), and feeding arteries and draining veins (in one), and discrimination between the venous sinus and tumor (in one). The anatomical information yielded by our technique makes safer surgery possible. If more detailed information which 3D-CTA cannot provide is required, our method should be performed.
To investigate whether DNA directly induces gastritis and/or peptic ulcer, we injected synthetic DNA including CpG motif (CpG-DNA) to mouse stomach. BALB/c mice were injected with either saline, acetic acid (AA), CpG-DNA, or Control-DNA. Mice were sacrificed, and sections of the stomachs were stained with hematoxylin and eosin. The lesions were histopathologically scored from 0 to 4 based on the extent of the inflammation. Populations of neutrophils and mononuclear cells infiltrated to the lesion were calculated. IFN-γ mRNA expression at the injection site was analyzed by RT-PCR. The number of CpG motifs included in the complete genomes of H. pylori HP26695 and J99, Escherichia coli O157, and Salmonella Typhi was determined by genomic analysis of these bacteria. Intragastric injection with CpG-DNA induced gastritis, and statistical analysis of histological scores revealed a significant difference between saline vs CpG-DNA (p=0.037). The population of mononuclear cells infiltrated to the lesions was significantly higher in mice injected with CpG-DNA than that injected with AA (p=0.0061). IFN-γ mRNA expression was detected in the CpG-DNA group. While H. pylori includes multiple CpG motifs in its genome, it has fewer than the other pathogenic gramnegative bacilli. We conclude that synthetic DNA including CpG motif directly causes gastritis in mice and induces IFN-γ production in the stomach. Bacterial DNA including CpG motif is known to stimulate innate immunity and to cause inflammation. Thus, H. pylori genomic DNA may be one of the virulent factors involved in H. pylori infection.
It is well known that unilateral profound sensorineural hearing loss is caused by mumps; however, bilateral deafness is rare. Herein we report a case of bilateral profound hearing loss caused by mumps infection in a four-year-old boy. Labyrinthitis due to the mumps virus was suspected. His verbal understanding was poor, and he completely stopped talking. He was soon fitted with a hearing aid, but it proved insufficient. Thereupon, cochlear implantation was performed on his left ear. Six months after the operation, his speech perception and speech production were improved. In cases of bilateral profound hearing loss due to mumps infection conservative therapy is ineffective; therefore, cochlear implantation is recommended. Vaccine coverage for mumps virus is also strongly recommended in Japan.