Spiral ganglion cell degeneration-induced deafness as a consequence of reduced GATA factor activity

Zinc-finger transcription factors GATA2 and GATA3 are both expressed in the developing inner ear, although their overlapping versus distinct activities in adult definitive inner ear are not well understood. We show here that GATA2 and GATA3 are co-expressed in cochlear spiral ganglion cells and redundantly function in the maintenance of spiral ganglion cells and auditory neural circuitry. Notably, Gata2 and Gata3 compound heterozygous mutant mice had a diminished number of spiral ganglion cells due to enhanced apoptosis, which resulted in progressive hearing loss. The decrease in spiral ganglion cellularity was associated with lowered expression of neurotrophin receptor TrkC that is an essential factor for spiral ganglion cell survival. We further show that Gata2 null mutants that additionally bear a Gata2 YAC (yeast artificial chromosome) that counteracts the lethal hematopoietic deficiency due to complete Gata2 loss nonetheless failed to complement the deficiency in neonatal spiral ganglion neurons. Furthermore, cochlea-specific Gata2 deletion mice also had fewer spiral ganglion cells and resultant hearing impairment. These results show that GATA2 and GATA3 redundantly function to maintain spiral ganglion cells and hearing. We propose possible mechanisms underlying hearing loss in human GATA2- or GATA3-related genetic disorders.

An isocenter detection and verification device for use in proton therapy

We developed a new device for isocenter detection and verification for use in proton therapy. This device can be used to confirm the isocenters of a room laser, a digital radiography system, and a rotational gantry. Agreement between the isocenters of a room laser and a digital radiography system was examined visually. We used the star-shots method for detecting and verifying the rotational gantry isocenter. The gafchromic film could be irradiated with this method using a 2 mm slitted 200 MeV proton beam. The isocenters of a room laser and digital radiography system were in good agreement. The size distribution of the isocenter by the star-shots method was <2 mm, which is the value recommended by the American Association of Physicists in Medicine Task Group 142. This new device can be used to evaluate comprehensive isocenter detection and verification for related equipment. Subsequent checking using this new device will decrease the uncertainty in measuring an isocenter. When using this device, the working time was significantly reduced to about 30 min, including preparation. These measurements should be useful for high accuracy daily treatments.

MafB is essential for renal development and F4/80 expression in macrophages

MafB is a member of the large Maf family of transcription factors that share similar basic region/leucine zipper DNA binding motifs and N-terminal activation domains. Although it is well known that MafB is specifically expressed in glomerular epithelial cells (podocytes) and macrophages, characterization of the null mutant phenotype in these tissues has not been previously reported. To investigate suspected MafB functions in the kidney and in macrophages, we generated mafB/green fluorescent protein (GFP) knock-in null mutant mice. MafB homozygous mutants displayed renal dysgenesis with abnormal podocyte differentiation as well as tubular apoptosis. Interestingly, these kidney phenotypes were associated with diminished expression of several kidney disease-related genes. In hematopoietic cells, GFP fluorescence was observed in both Mac-1- and F4/80-expressing macrophages in the fetal liver. Interestingly, F4/80 expression in macrophages was suppressed in the homozygous mutant, although development of the Mac-1-positive macrophage population was unaffected. In primary cultures of fetal liver hematopoietic cells, MafB deficiency was found to dramatically suppress F4/80 expression in nonadherent macrophages, whereas the Mac-1-positive macrophage population developed normally. These results demonstrate that MafB is essential for podocyte differentiation, renal tubule survival, and F4/80 maturation in a distinct subpopulation of nonadherent mature macrophages.

Primitive erythropoiesis from mesodermal precursors expressing VE-cadherin, PECAM-1, Tie2, endoglin, and CD34 in the mouse embryo

Vascular endothelial (VE) cadherin, PECAM-1 (platelet endothelial cell adhesion molecule-1, CD31), Tie2, CD34, and endoglin are established markers for adult and embryonic endothelial cells (ECs). Here, we report that the expression of these EC markers is initiated in the extraembryonic region at the late-streak stage (nominal stage E6.75). Immunohistochemical analysis shows that EC marker-positive cells arise in a subset of Flk1 (VEGF-R2) mesodermal cells. In contrast, GATA1, a marker for primitive erythropoietic progenitors, is expressed in a more restricted subset of Flk1-positive cells. Using flow cytometry, we observed that the GATA1-positive cell population existed as a subset of the EC marker-positive cell. Consistent with this notion, we showed with the primitive hematopoietic colony assay that primitive erythropoietic progenitors are enriched in PECAM-1- and Tie2-positive cells. These results suggest that primitive hematopoietic cells arise from EC marker-positive cells. Thus, VE-cadherin, PECAM-1, CD34, endoglin, and Tie2 are expressed not only in adult and embryonic ECs but in extraembryonic Flk1-positive cells during gastrulation. The latter cell population includes progenitors that give rise to primitive hematopoietic cells, suggesting that primitive and definitive hematopoietic cells in the mouse embryo arise from EC marker-positive cells.

Effect of acoustic stress on glucocorticoid receptor mRNA in the cochlea of the guinea pig

As a first step toward elucidating the mechanism underlying the therapeutic effect of glucocorticoids on acute noise-induced hearing loss, we used semiquantitative reverse transcription polymerase chain reaction to study the level of glucocorticoid receptor (GR) mRNA in the cochlea of the guinea pig after acoustic overstimulation. The cochleas were dissected and divided into three portions (lateral portion, medial portion and modiolus). In the lateral portion, the glucocorticoid receptor mRNA level was significantly decreased 2 h after exposure to a 120 dB SPL sound and both 2 and 6 h after exposure to a 130 dB SPL sound. To determine where in the cochlea the changes in glucocorticoid receptor mRNA levels occur, in situ hybridization histochemistry was performed with digoxigenin-labeled sense and antisense RNA probes complementary to guinea pig glucocorticoid receptor mRNA. Glucocorticoid receptor mRNA was demonstrated in the spiral ligament, stria vascularis, spiral limbus and spiral ganglion. Moreover, the glucocorticoid receptor mRNA level was decreased in the spiral ligament, especially in the spiral prominence of the basal turn, 2 h after exposure to the 130 dB SPL sound. These results could imply that the therapeutic effect of glucocorticoids in the cochlea might be mediated in the spiral ligament, particularly in the spiral prominence.

Activation of mu-opioid pathway is associated with the canceling effect of footshock stimulus on the restraint stress-induced inhibition of small intestinal motility in rats

We previously reported that small intestinal motility was significantly inhibited by restraint stress, but not by footshock stress. In the present study, we found that plasma beta-endorphin levels were more significantly elevated by footshock stress than restraint stress, and that preloading of footshock stimulus canceled the inhibition of small intestinal motility by restraint stress. Pretreatment with the mu-opioid receptor antagonist naltrexone significantly attenuated this canceling effect of footshock stimulus. These results suggest that footshock stimulus may cancel the inhibition of small intestinal motility by restraint stress via activation of mu-opioid receptors.

Effect of acoustic overstimulation on regulation of glucocorticoid receptor mRNA in the cochlea of the guinea pig

Semi-quantitative reverse transcription polymerase chain reaction was performed to determine the distribution of mRNA levels of glucocorticoid receptor (GR) within the guinea pig cochlea and to examine the change in their expression after acoustic overstimulation. Using an original PCR primer for the guinea pig, the highest GR mRNA level was revealed in the modiolus and lowest in the medial portion including the organ of Corti. Total RNA was extracted from the whole cochlea of the guinea pig 0, 2, 6 and 24 h after exposure to a 2 kHz pure tone of 110, 120 or 130 dB SPL for 10 min. The level of GR mRNA significantly decreased immediately and 2 h after exposure to the sound of 120 dB SPL, and 2 and 6 h after exposure to that of 130 dB SPL. These results suggest the presence of a down-regulation of GR mRNA induced by acoustic overstimulation, although the exact mechanism of this phenomenon remains unsolved.

Multi-layer energy filter for realizing conformal irradiation in charged particle therapy

A new type of filter for charged particle radiotherapy is developed to reduce unwanted dose transfer to the normal tissues around a tumor. The new filter can make a static irradiation field where the width of the spread-out Bragg peak (SOBP) is two-dimensionally adjusted. That makes the field conformal to the tumor three-dimensionally. The filter is made of many layers produced by using stereolithography. The layer has a miniaturized structure that has geometrical similarity to the conventional ridge filter. Shapes of cone and pyramid are also usable for the unit-cell constructing the layer. The spread of the field in the depth direction is decided by the thickness of the filter, or by the number of layers. The experimental result of the irradiation using the ridge-type construction shows a good agreement with an estimate by the Monte Carlo calculation. By combining this technique with intensity modulation that has lateral position dependence, the conformal irradiation can be achieved by a simple procedure.