Kanamycin ototoxicity in glutamate transporter knockout mice

Glutamate-aspartate transporter (GLAST), a powerful glutamate uptake system, removes released glutamate from the synaptic cleft and facilitates the re-use of glutamate as a neurotransmitter recycling system. Aminoglycoside-induced hearing loss is mediated via a glutamate excitotoxic process. We investigated the effect of aminoglycoside ototoxicity in GLAST knockout mice using the recorded auditory brainstem response (ABR) and number of hair cells in the cochlea. Kanamycin (100 mg/mL) was injected directly into the posterior semicircular canal of mice. Before the kanamycin treatment, there was no difference in the ABR threshold average between the wild-type and knockout mice. Kanamycin injection aggravated the ABR threshold in the GLAST knockout mice compared with the wild-type mice, and the IHC degeneration was more severe in the GLAST knockout mice. These findings suggest that GLAST plays an important role in preventing the degeneration of inner hair cells in aminoglycoside ototoxicity.     

Impact of prior lamivudine use on the antiviral efficacy and development of resistance to entecavir in chronic hepatitis B patients

Background/Aims

To determine the efficacies of entecavir (ETV) in nucleos(t)ide analogue (NA)-naïve chronic hepatitis B (CHB) patients and in those with prior lamivudine (LAM) use who did not develop resistance.

Methods

We retrospectively enrolled 337 patients with CHB who were treated with ETV (0.5 mg daily) for at least 30 months. The study included 270 (80.1%) NA-naïve patients and 67 (19.9%) LAM-use patients. Ten of the LAM-use patients were refractory to LAM therapy without developing resistance.

Results

Genotypic resistance to ETV developed more frequently in the LAM-use group (13.1%) than in the NA-naïve group (2.6%) at 60 months (P=0.009). In subgroup analysis, after excluding the 10 patients who were refractory to LAM therapy, the cumulative probability of ETV resistance did not differ significantly between the two groups (P=0.149). Prior LAM refractoriness and a higher hepatitis B virus DNA level at month 12 were independent predictive factors for the development of ETV resistance.

Conclusions

ETV resistance developed more frequently in LAM-use patients with CHB. However, prior LAM use without refractoriness did not affect the development of ETV resistance. The serum hepatitis B virus DNA level at month 12 was a major predictor for the development of ETV resistance.     

Localization of prosaposin in rat cochlea

Prosaposin, the precursor of the sphingolipid hydrolase activator proteins called saposins A, B, C, and D, is abundant in the nervous system and muscles. Besides its role as the precursor of saposins, prosaposin is reported to function as a neurotrophic factor, initiating neural differentiation and preventing neuronal cell death in vivo and in vitro. In this study, we examined the localization and synthesis of prosaposin in the rat cochlea. Intense prosaposin immunoreactivity was observed in the organ of Corti, stria vascularis, and spiral ganglion. In an immuno-electron microscopic study, prosaposin immunoreactivity was found mainly in lysosomal granules of the cells in these regions. In the lysosome, prosaposin does not always colocalize with cathepsin D, but was localized mainly in the dark area of the lysosome. Prosaposin mRNA was observed in these same regions. Our results suggest that prosaposin plays a role in homeostasis in the peripheral auditory system.     

Prognostic Significance of Immunohistochemically Detected Blood and Lymphatic Vessel Invasion in Colorectal Carcinoma: Its Impact on Prognosis

Background The prognostic significance of blood vessel invasion (BVI) and lymphatic vessel invasion (LVI) is unclear. Because of the absence of specific markers for venous and lymphatic vessels, earlier studies could not reliably distinguish between BVI and LVI. Methods By immunostaining for podoplanin and CD34 antigen, we retrospectively investigated LVI and BVI in 419 tissue specimens of colorectal carcinoma. We performed univariate and multivariate analysis of the clinicopathologic features, frequency of recurrence, and outcome of patients with or without LVI and BVI. Results The use of hematoxylin and eosin (H&E) staining to identify BVI and LVI yielded a false positive rate of 9.1% and false negative rate of 12.6%. The incidence of BVI was significantly higher among tumors with LVI than tumors without LVI (P <.001). In logistic multivariate analysis, only LVI (P < .001) was associated with lymph node metastasis and BVI (P = .015) was associated with distant recurrence. Calculating the prognostic relevance, both two invasion types correlated with decreased survival in univariate analysis (both P <.001). In multivariate analysis, BVI (P =.024), lymph node status (P =.003) and tumor stage (P <.001) remained statistically significant factors for survival. Conclusions Our results suggest that immunohistologic evaluation of BVI and LVI could be useful in colorectal carcinoma indicating the risk of lymph node metastasis and recurrence, thereby contributing to prognostic evaluation.     

Transient cochlear ischemia causes delayed cell death in the organ of Corti: an experimental study in gerbils

To elucidate whether ischemia-reperfusion can cause delayed cell death in the cochlea, the effects of transient cochlear ischemia on hearing and on neuronal structures in the cochlea were studied in Mongolian gerbils. Ischemia was induced by bilaterally occluding the vertebral arteries for 5 minutes in gerbils, which lack posterior cerebral communicating arteries. In gerbils, the labyrinthine arteries are fed solely by the vertebral arteries. Occlusion of the vertebral arteries caused a remarkable increase in the threshold of compound action potentials (CAPs), which recovered over the following day. However, 7 days after the onset of reperfusion, the threshold began to increase again. Morphologic changes in the hair cell stereocilia were revealed by electron microscopy. The number of nuclear collapses was counted in cells stained for DNA and F-actin to evaluate the degree of cell death in the organ of Corti. Changes in spiral ganglion cell (SGC) neuron number were detected, whether or not progressive neuronal death occurred in the SGC. These studies showed that sporadic fusion of hair cells and the disappearance of hair cell stereocilia did not begin until 4 days after ischemia. On subsequent days, the loss of hair cells, especially inner hair cells (IHCs), and the degeneration of SGC neurons became apparent. Ten days after ischemia, the mean percentage cell loss of IHCs was 6.4% in the basal turn, 6.4% in the second turn, and 0.8% in the apical turn, respectively, and the number of SGC neurons had decreased to 89% of preischemic status. These results indicate that transient ischemia causes delayed hearing loss and cell death in the cochlea by day 7 after ischemia.     

Demyelination associated with HSV-1-induced facial paralysis

In 1995, we developed an animal model of transient homolateral facial nerve paralysis by inoculating Herpes simplex virus type 1 (HSV-1) into the auricle of mice. This study examined the mechanism of facial nerve paralysis in this model histopathologically. Using the immunofluorescence technique with anti-HSV-1 antibody, the time course of viral spread and the site of viral replication were investigated over the entire course of the facial nerve. Furthermore, viral replication and nerve degeneration at the site of viral replication were observed by electron microscopy. On the 7th day after inoculation, facial paralysis was observed in more than 60% of mice. Immunofluorescence study revealed HSV-1 in the geniculate ganglion, the descending root, and the facial nucleus at this stage. On the 9th day, the descending root in the sections stained with osmium looked pale, because prominent demyelination had occurred in this region; electron micrographs showed many degenerated oligodendrocytes and large naked axons. In contrast, the facial nucleus neurons showed no remarkable degeneration, despite HSV-1 particles in their cytoplasm. From these findings, we concluded that facial nerve paralysis in this model is caused mainly by facial nerve demyelination in the descending root.