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.     

Modification of the radial procedure in a patient with partial atrioventricular septal defect

We successfully cured atrial fibrillation while preserving internodal conduction in a patient with a partial atrioventricular septal defect. Because the anterior and middle internodal tracts are interrupted by the defect, the lower right atrial incision of either the maze or the radial procedure may interrupt the remaining posterior tract, resulting in internodal conduction block. We deleted the posterior septal incision from the radial procedure and replaced it with a right-side left atriotomy. The patient resumed normal sinus rhythm with significant contraction of the right and left atria. The preserved internodal pathway through the posterior interatrial septum was confirmed by electrophysiologic study.     

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.     

Centrifugal lipodystrophy presenting with serpiginous erythema and alopecia

We describe serpiginous erythema with alopecia developing on the scalp of a 10-year-old boy during follow-up of centrifugal lipodystrophy. Because the clinical and histopathologic features of these lesions were identical to those of centrifugal lipodystrophy, we conclude that involvement of a hairy region by this disorder could cause alopecia and that the hair loss might be an indirect effect of interstitial inflammatory infiltrates around the hair follicles and in the subcutaneous fat.     

Role of tissue plasminogen activator in the rewarding effect of morphine]

Tissue plasminogen activator (tPA) is a serine protease that catalyzes the conversion of plasminogen (plg) to plasmin. The tPA-plasmin system plays a role in synaptic plasticity and remodeling. In this review, we focused on the role of tPA-plasmin system in the rewarding effect of morphine. A single morphine treatment induced tPA mRNA and protein expression in a naloxone-sensitive manner, which was associated with an increase in the enzyme activity in the nucleus accumbens (NAc). The acute effect of morphine in inducing tPA expression was diminished after repeated administration. No differences were observed in the morphine-induced antinociceptive effect between wild-type and tPA knockout (tPA-/-) mice. Morphine-induced conditioned place preference and hyperlocomotion were significantly reduced in tPA-/- and pLg-/- mice, being accompanied by a loss of morphine-induced dopamine release in the NAc. Microinjection of either exogenous tPA or plasmin into the NAc significantly potentiated morphine-induced dopamine release in the NAc of ICR mice. In contrast, plasminogen activator inhibitor-1 (PAI-1) dose-dependently reduced morphine-induced dopamine release. Furthermore, the defect of morphine-induced dopamine release and hyperlocomotion in tPA-/- mice was reversed by microinjections of either exogenous tPA or plasmin into the NAc. Our findings demonstrate a novel function of the tPA-plasmin system in regulating dopamine release in the NAc, which is involved in the morphine reward.     

Cell-free Human T-cell Leukemia Virus Type 1 Binds to, and Efficiently Enters Mouse Cells

Human T-cell leukemia virus type 1 (HTLV–1) is an etiologic agent of adult T-cell leukemia/lymphoma and other HTLV-1–associated diseases. However, the interaction between HTLV–1 and T cells in the pathogenesis of these diseases is poorly understood. Mouse cells have been reported to be resistant to cell-free HTLV–1 infection. However, we recently reported that HTLV–1 DNA could be observed 24 h after cell-free HTLV–1 infection of mouse cell lines. To understand HTLV–1 replication in these cells in detail, we concentrated the virus produced from c77 feline kidney cell line and established an efficient infection system. The amounts of adsorption of HTLV–1 are larger in mouse T cell lines, EL4 and RLml, than those in human T cell lines, Molt4 and HUT78, and are similar to that in human kidney cell line, 293T. Unexpectedly, however, the amounts of entry of HTLV–1 are about 10–fold larger in the two mouse cell lines than those in the three human cell lines employed. Moreover, viral DNA was detectable from 1 h in EL4 and RLml cells, but only from 2–3 h in 293T, Molt4 and HUT78 cells. However, the amount of viral DNA in EL4 cells became smaller than that in Molt4 cells. HTLV–1 expression could be detected until day 1–2 in RLml and EL4 cells, and until day 4 in Molt4 cells. Our results suggest that mouse cell experiments would give useful information to dissect the early steps of cell-free HTLV–1 infection.     

Inhibitory effect of liposomal MDP-Lys on lung metastasis of transplantable osteosarcoma in hamster

MDP-Lys (N2-[(N-acetylmuramyl)-L-alanyl-D-isoglutaminyl]-N6-stearoyl-L-lysine), a macrophage activator, is a lipophilic derivative of muramyl dipeptide (MDP). Multilamellar liposome incorporated MDP-Lys was prepared using phosphatidylcholine and phosphatidylserine by conventional film method, and its inhibitory effect on lung metastasis was compared with MDP-Lys as a solution in hamster's osteosarcoma. The lung metastatic rates after transplantation of the tumor to a lower extremity, in which the extremity was amputated 3 weeks later, were 50% and 100% 3 and 7 weeks, respectively, after transplantation. The rates after amputation were reduced by the treatment with MDP-Lys proportionally to the logarithmic MDP-Lys dose, and the rates 7 weeks after transplantation were 55% and 60%, respectively, in the MDP-Lys solution (50 microg/day) and liposomal MDP-Lys (20 microg twice/week) groups. Fifty percent of hamsters treated with liposomal MDP-Lys survived for more than 6 months. Considering that hamsters had a lung metastasis rate of 50% before MDP-Lys treatment, liposomal MDP-Lys given at a dose of 20 microg twice/week was effective for inhibiting lung metastasis at a far lower dose of MDP-Lys than that given as a solution (40 microg vs. 350 microg per week). No significant side effect of liposomal MDP-Lys, as evaluated by the comparison of body weight changes among differently treated hamsters, was detected. This greater inhibitory effect of liposomal MDP-Lys can be considered to be due to the longer retention of the liposomal form in the lung.     

Fluctuations of the Hemodynamic Derivatives During Left Ventricular Assistance Using Oscillated Blood Flow

Abstract: To analyze the autonomic nervous system during left heart bypass with a vibrating flow pump (VFP), fluctuations in hemodynamic derivatives were evaluated by the spectral analysis method using fast fourier transform methodology. After the left pleural cavity was opened through the fourth intercostal space under general anesthesia, a VFP was implanted as the left heart bypass device in chronic animal experiments using 3 healthy adult goats. Hemodynamic parameters with and without VFP assistance were recorded on magnetic tape in awake animals and were analyzed by computer through an analog to digital convertor. Power spectral analysis was performed on a beat-to-beat basis for the evaluation of the fluctuations. During left heart bypass with the VFP, Mayer wave fluctuations were decreased significantly although respiratory waves were not changed significantly. These results suggest that sympathetic nervous system modulation was changed under the influences of the left heart bypass with VFP. By using this analysis methodology, truly physiologic ventricular assistance may be achieved.