Germline recruitment in mice: a genetic program for epigenetic reprogramming.

Germ cells provide an enduring link between generations and therefore must possess the fundamental ability of reprogramming their genome to generate a totipotent state. We wish to understand the molecular basis of the unique properties of the mammalian germ line. Recently we identified Blimp1, a potent transcriptional repressor of a histone methyltransferase subfamily, as a critical determinant of the germ cell lineage in mice. Surprisingly, Blimp1 expression marks the origin of the germ line in proximal epiblast cells in pregastrulation embryos, substantially earlier than previously thought. Furthermore, we showed that established primordial germ cells undergo extensive erasure of genome-wide histone H3 lysine 9 dimethylation (H3K9me2) and DNA methylation, two major repressive epigenetic modifications, and instead acquire high levels of H3-K27 trimethylation (H3K27me3) in their migration period. We suggest that germline specification is a genetic system for the orderly reprogramming of the cells' epigenome toward a totipotent state, with reacquisition of totipotency-associated transcription factors and continued Blimp1 expression preventing their reversion to an explicit pluripotent state or somatic differentiation.

Intense noise induces formation of vasoactive lipid peroxidation products in the cochlea.

This study investigates the correlation between the formation of reactive oxygen species (ROS) and auditory damage in noise-induced hearing loss. The noise exposure (4-kHz octave band, 115 dB SPL, 5 h) created permanent threshold shifts at frequencies from 2 to 20 kHz. The lipid peroxidation product, 8-isoprostane, was determined biochemically and histochemically as an indicator of ROS. Noise exposure increased 8-isoprostane levels in the cochlea in a time-dependent manner. After 5 h of exposure, 8-isoprostane levels were more than 30-fold greater than baseline, and decreased rapidly after the termination of noise. The immunoreactivity to 8-isoprostane was increased in the stria vascularis, spiral ganglion cells and the organ of Corti. In the organ of Corti, immunostaining was restricted to the second turn in a region 10-12 mm from the apex. This region sustained most of the permanent hair cell damage as revealed in surface preparations. Outer hair cells were more heavily immunostained than inner hair cells while Hensen's cells showed still less immunostain. These data are consistent with the view that ROS are involved in noise-induced damage. However, the relationship between ROS formation and tissue damage appears complex. In the organ of Corti, the pattern of noise-induced lipid peroxidation correlates well with subsequent morphological damage. The stria vascularis, however, does not sustain permanent damage despite intense lipid peroxidation. Differences in endogenous antioxidant levels and commitment to different apoptotic or survival pathways may underlie such differential responses.

Glutathione limits noise-induced hearing loss.

The generation of reactive oxygen species (ROS) is thought to be part of the mechanism underlying noise-induced hearing loss (NIHL). Glutathione (GSH) is an important cellular antioxidant that limits cell damage by ROS. In this study, we investigated the effectiveness of a GSH supplement to protect GSH-deficient animals from NIHL. Pigmented guinea pigs were exposed to a 4 kHz octave band noise, 115 dB SPL, for 5 h. Group 1 had a normal diet, while groups 2, 3 and 4 were fed a 7% low protein diet (leading to lowered tissue levels of GSH) for 10 days prior to noise exposure. One hour before, immediately after and 5 h after noise exposure, subjects received either an intraperitoneal injection of 5 ml/kg body weight of 0.9% NaCl (groups 1 and 2), 0.4 M glutathione monoethyl ester (GSHE; group 3) or 0.8 M GSHE (group 4). Auditory thresholds were measured by evoked brain stem response at 2, 4, 8, 12, 16 and 20 kHz before and after noise exposure. Ten days post exposure, group 1 showed noise-induced threshold shifts of approximately 20 dB at 2, 16 and 20 kHz and 35 to 40 dB at other frequencies. Threshold shifts in group 2 were significantly greater than baseline at 2, 4, 16 and 20 kHz. GSHE supplementation in a dose-dependent fashion attenuated the threshold shifts in the low protein diet animals. Hair cell loss, as evaluated with cytocochleograms, was consistent with the auditory-evoked brainstem response results. Group 2 exhibited significantly more hair cell loss than any of the other groups; hair cell loss in group 3 was similar to that seen in group 1; group 4 showed less loss than group 1. These results indicate that GSH is a significant factor in limiting noise-induced cochlear damage. This is compatible with the notion that ROS generation plays a role in NIHL and that antioxidant treatment may be an effective prophylactic intervention.

Blood flow in common carotid and vertebral arteries in patients with sudden deafness.

Blood flow was measured in the common carotid artery (CCA) and the vertebral artery (VA) by the ultrasonic Doppler method in 14 male patients with sudden deafness and 70 normal adults. In the patients, blood flow on the affected side was slower than that on the normal side or that of the control group. Although these differences were not statistically significant in the CCA or in the VA, significant differences in the blood flow were noted between the group with a hearing loss of greater than 50 dB and the group with a loss of less than 50 dB. A negative correlation was found between blood viscosity and blood flow in both CCAs and both VAs. After stellate ganglion block (SGB), the blood flow of the CCA and VA increased on the side of the SGB and decreased on the opposite side. The changes in blood flow after SGB decreased with age, presumably because of changes in the blood vessel walls and a weaker response to sympathetic nerve receptors in the arterial wall.

Influence of hypotension on cochlear blood flow in polycythemic condition.

We examined the influence of hypotension by infusion of acebutolol hydrochloride (AH), a cardioselective beta-receptor antagonist, on cochlear blood flow in guinea pigs with various hematocrit values. AH infusion lowered the mean blood pressure to almost the same degree in all animals, regardless of the hematocrit level. The degree of the concomitant decrease of CBF varied with the hematocrit, being greater in animals with a higher hematocrit. In those with the highest hematocrit CBF did not return to the initial level. From these values we calculated the O2 transport capacity after AH infusion and found it to be lower than in animals without AH infusion. The difference was greater at higher hematocrits. These findings suggest that the microcirculation of the inner ear is responsive to transient decreases of perfusion pressure at high hematocrits.

Effects of pentoxifylline and nitroprusside on guinea pig cochlear blood flow in relationship to various hematocrit values.

To understand better the microcirculation in the inner ear in relation to blood viscosity, we examined the effects of pentoxifylline (PXF) and nitroprusside (NP) on cochlear blood flow (CBF) in healthy adult guinea pigs in relationship to various hematocrit (H1) values. There was no correlation between Ht value and the maximum decrease of mean blood pressure after PXF infusion, whereas there was a positive correlation between Ht and the maximum increase in CBF. No such relationship was found after NP infusion. A graph plot of each animal's blood oxygen transport capacity (i.e., Ht/blood viscosity) was found to have a convex form and to increase with a shift of the peak to a higher Ht area after PXF infusion. These findings indicate that a decrease in blood viscosity may improve CBF and increase oxygen transport capacity of blood.

Effects of hyperventilation and hypoventilation on cochlear blood flow and endocochlear direct-current potential.

To understand the importance of oxygen transport to the inner ear tissue, we studied, in guinea pigs, the relationship between cochlear blood flow and endocochlear direct-current potential (EP) under different respiratory conditions. EP, a functional parameter of the stria vascularis, was recorded by a microelectrode inserted into the lateral wall of the chochlea. To measure the cochlear blood flow (CoBF), we employed laser Doppler flowmetry and recorded the flow with a probe placed on the same spot on the lateral wall. During 3 min of asphyxia, CoBF and systemic blood pressure showed irregular biphasic increases, while the EP decreased to reach a negative value. In the hypoxemia experiment, which was induced by stepwise reduction of the respiratory rate to 60%, increases in CoBF and blood pressure were evident during hypoventilation with an intermediate position of EP in the positive range. The mechanisms of these increases in two parameters are discussed from the viewpoints of sympathicotonic activity in the autonomic nervous system and the vasodilating action of CO2 during hypercapnia. In the hyperoxemia experiment, which was induced by stepwise increase in the respiratory rate to 140%, CoBF and blood pressure were found to decrease during hyperventilation with no significant change of EP. The decrease in blood pressure was considered to be due to the increase in intrathoracic pressure caused by the increased rate of artificial respiration. As for the concomitant decrease in CoBF, chemical regulation of PCO2 in the vascular bed of the lateral wall of the cochlea was thought to be a contributory factor.

Blood viscosity and plasma viscosity in patients with sudden deafness.

Blood viscosity and plasma viscosity were measured in 51 patients with sudden deafness (SD) and 70 controls with normal hearing. Blood viscosity and plasma viscosity in patients with SD at their first medical examination were significantly higher than in the control group. The difference in viscosimetry results between the two groups was greater at higher shear rates. The data obtained in viscosimetry and pure-tone audiometry were analyzed after dividing the patients into a high viscosity group and a normal viscosity group. The correlation between average hearing level in pure-tone audiogram and blood viscosity or plasma viscosity was positive. The values of the O2-transport capacity of the blood demonstrated a negative correlation with average hearing level in patients with SD before treatment. During the course of treatment, blood viscosity and plasma viscosity decreased with the improvement of hearing impairment. When the distribution of average hearing level was 40 to 79 dB, a few of the patients with "recovery" or "good improvement" and most of patients with "fair improvement" or "no change" belonged to the low viscosity group. And, most of the patients with flat type hearing impairment and a few patients with high tone type hearing impairment belonged to the high viscosity group. These results suggest that many patients with SD have increased blood viscosity and plasma viscosity, and that this increase may play a significant role in the etiology of SD. There are also some differences in etiologic factors concerning type of hearing impairment and prognosis. In conclusion, the present study points to the importance of measuring blood viscosity and plasma viscosity in patients with SD, since blood and/or plasma viscosity may be involved in its etiology and prognosis.

[Human herpesvirus-6 antibodies in idiopathic facial nerve palsy and sudden deafness].

Human herpesvirus-6 (HHV-6) is the causative agent for exanthem subitum. This study investigated the relationship between idiopathic facial nerve palsy (Bell's palsy), sudden deafness and HHV-6 infection. Both Bell's palsy and sudden deafness are syndromes which causes are unknown. Both of them are suspected viral infection as causative agents. Paired sera from 22 patients of Bell's palsy and 39 patients of sudden deafness were examined for reactivity to HHV-6 by the indirect immunofluorescence test. On a case of Bell's palsy and two cases of sudden deafness each of the HHV-6 antibody titers was increased.

Subarachnoid hemorrhage and spinal root injury caused by acupuncture needle--case report.

The authors report a case of subarachnoid hemorrhage and spinal root injury caused by an acupuncture needle buried in the posterior neck about 30 years before onset. A 33-year-old female presented with sudden onset of severe occipital headaches. Plain x-ray films of the cervical spine revealed a fine gold needle, about 1.5 cm in length, between the C1 and C2 vertebrae. The needle was piercing the spinal nerve root through the dural vein, and was removed. Postoperatively, the pain exacerbated by neck movement disappeared.