Clinical evaluation of a portable digital hearing aid with narrow-band loudness compensation

A new portable digital hearing aid referred to as CLAIDHA (Compensate for Loudness by Analyzing Input-signal Digital Hearing Aid), which employs frequency-dependent amplitude compression based on narrow-band loudness compensation, was clinically evaluated in 159 subjects with hearing loss. The results of speech tests revealed better intelligibility compared with the subject's own hearing aids; the advantage of using CLAIDHA in daily life was also indicated by the results of a questionnaire completed by the subjects. In about 64% of the subjects with a flat, gradually sloping type of hearing loss, CLAIDHA was satisfactorily adopted for daily use. However, in the subjects with a steeply sloping type of hearing loss and subjects with losses mainly at high and low frequencies, with near-normal mid-frequency hearing. this loudness compensation scheme seems to be slightly less effective.

[FLAIR images of mild head trauma with transient amnesia]

A newly advanced MRI pulse sequence, the FLAIR (fluid-attenuated inversion recovery) imaging, in which a long TE spin echo sequence is used with suppression of the CSF with an inversion pulse, displays the CSF space as a no signal intensity area. We examined 45 cases of mild head trauma with posttraumatic amnesia by FLAIR images and could detect some findings which could not be detected by CT scan and conventional MR images. These findings could be detected in many patients with long post-traumatic amnesia (over 2 hours), but they could not be detected in patients with short posttraumatic amnesia (within 30 mins). These findings existed surrounding lateral ventricles and we classified them into 3 types: type 1 is anterior horn of lateral ventricle, type 2 is the base of frontal lobe, type 3 is cerebral deep white matter. Some of them were examined again by FLAIR images a month later, and these findings had disappeared. We suspect that these lesions were brain edema or mild contusion without hemorrhage.

Measurement of RBC velocities in the rat pial arteries with an image-intensified high-speed video camera system

The mean centerline red blood cell (RBC) velocity of the rat pial artery was measured using an image-intensified high-speed (1000 frames/s) video camera system and RBCs labeled with fluorescein isothiocyanate (FITC). Some investigations measuring RBC velocity have been made in most organs, but the RBC velocity of the pial artery has not yet been measured with this system using FITC labeled RBC. After recording the emission of the FITC labeled RBC through a closed cranial window using this system, the authors analyzed the videotape. The movement of each individual RBC for several milliseconds over a distance of 50 microm could be pursued. The mean centerline RBC velocity in normal rats varied between 1.0 and 9.0 mm/s (most of the measurements we taken in vessels ranging between 20 and 80 microm in diameter). As the diameter of the pial artery becomes smaller, the blood flow rate (pi x (diameter/2)2 x (mean centerline velocity/1.6)) tends to become smaller. During CO2 inhalation, the pial artery diameter, mean centerline RBC velocity, and blood flow rate increased with statistical significance. Mean centerline RBC velocities in the cerebral microcirculation could not be measured directly with accuracy using the older methods (30 frames/s). However, this method is useful for investigation of the cerebral microcirculation and is considered to be applicable for studying the behavior of leukocytes or platelets, which will be examined in a subsequent study.

Acute effects of combined administration of kanamycin and furosemide on the stria vascularis studied by distortion product otoacoustic emission and transmission electron microscopy

Acute effects of kanamycin and/or furosemide administration on the stria vascularis of the guinea pig cochlea were assessed by distortion product otoacoustic emission (DPOAE) and transmission electron microscopy. Kanamycin alone failed to affect the DPOAE levels and ultrastructural changes. Furosemide alone caused a rapid but reversible fall of the DPOAE levels. No remarkable pathological changes in the strial vascularis were observed after a complete recovery of the DPOAEs. On the other hand, furosemide injection following kanamycin with a 2 hour interval resulted in two patterns of significant changes in the DPOAEs, namely, a sudden drop in the DPOAE levels 2 to 3 hours after furosemide injection and a gradual fall in the DPOAE levels immediately after the incomplete recovery from the furosemide-induced decrease of the DPOAE levels. Ultrastructural changes in the stria vascularis included numerous vacuoles in the strial marginal cells and increased electron density of the intermediate and basal cells. These physiological and morphological changes in the stria vascularis may imply new ototoxic features induced by kanamycin potentiated by furosemide.

In situ phosphorylation of bone and dentin proteins by the casein kinase II-like enzyme

Our previous studies suggested the possibility of extracellular phosphorylation of matrix phosphoproteins into more phosphorylated forms by mature odontoblasts and osteocytes (Mikuni-Takagi et al., 1995; Satoyoshi et al., 1995). To elucidate such phosphorylation of bone and dentin proteins, we developed a histochemical method using frozen sections to determine the sites of enzymatic processing by the casein kinase II-like enzyme. It was observed that proteins in bone, dentin, and predentin are phosphorylated by the endogenous enzyme when the tissue slices were incubated with [gamma-32P] GTP, suggesting that there are both substrates and the enzyme in these matrices. In vivo, phosphate donors, ATP and GTP, may be supplied through dentinal canals and osteocyte canaliculi. Immunohistochemical analysis of frozen sections showed that the extremely intense staining of phosphoserine residues by anti-phosphoserine antibodies appeared in dentin only after demineralization of the tissue samples. It implies that these phosphoserine residues become bound to mineral as soon as the phosphorylation is completed, thereby being inaccessible to the antibodies without demineralization. The data support our notion that the extracellular phosphorylation of dentin/bone proteins, regulated by the developmental stages of bone and dentin cells, occurs prior to matrix mineralization.

[Analysis of abnormal findings observed on brain MRI T 2 weighted image in a system for the detection of asymptomatic brain disease in 1,200 cases]

In this study we described the significance of asymptomatic cerebral infarction (ACI) and periventricular hyperintensity (PVH) observed on brain MRI in a system for detection of asymptomatic brain disease with 1,200 cases. The risk factors (RF), population in each age bracket of ACI and PVH, among groups with hypertension (HTG) and without RF (no-RFG), were investigated. The RF of ACI were hypertension (HT), diabetes mellitus (DM), and aging. Without DM, those are common RF of PVH. The population of PVH and ACI with PVH increased with aging in no -RFG. On the other hand, only the population of ACI with PVH increased with aging in HTG. The rate of these abnormal findings in HTG was significantly higher than that in no-RFG. In addition, HT accelerated the occurrence of these findings by 10-20 years. When patients were over 60 years old, ACI increased rapidly. Accordingly, we concluded that (1) PVH and ACI had a common background. (2) Long term follow up concerning the incidence of ACI in the group with only PVH was necessary. (3) It was desirable that treatment for RF should be effected before the age of sixty.

Calcitonin gene-related peptide stimulates potassium efflux through adenosine triphosphate-sensitive potassium channels and produces membrane hyperpolarization in osteoblastic UMR106 cells

In previous studies, we have shown that calcitonin gene-related peptide (CGRP) acutely inhibits 45Ca2+ uptake in osteoblastic UMR106 cells, and we have proposed that ATP-sensitive potassium (K(ATP)) channels are involved in mediating this action of CGRP. To directly test this proposed mechanism, we have now examined the effects of CGRP on both membrane potential (Em) and K+ mobilization in UMR106 cells, using specific fluorometric dye assays. CGRP (0.01-100 nM) induced membrane hyperpolarization in a dose-dependent manner, with a half maximal effect (ED50) at approximately 0.2 nM and a maximal effect at 100 nM. Both pinacidil (Pina; a K(ATP) channel opener) and forskolin (FSK) induced similar membrane hyperpolarization, but the actions of these three agents could be easily distinguished: both CGRP and Pina actions were well antagonized by glibenclamide (Glib; a selective K(ATP) channel blocker), whereas FSK action was strongly attenuated only by tetraethylammonium (a K(Ca) channel blocker) or compound H-89 (an inhibitor of cAMP-dependent protein kinases). Cells pretreated with Pina no longer responded to CGRP, but they could still respond to FSK; furthermore, pretreatment with FSK failed to block successive treatment with either CGRP or Pina. In parallel with observed changes in Em, CGRP (0.01-100 nM) decreased intracellular K+ concentrations ([K+]i) in a dose-dependent manner, with an ED50 identical to that obtained for alterations in Em. This action of CGRP was sensitive to Glib and had only slight sensitivity to tetraethylammonium; this CGRP effect was mimicked by Pina but not by FSK. Interestingly, CGRP significantly elicited changes in cell shape by a Glib-sensitive mechanism that included notable decreases in cross-sectional cytoplasmic area. These observations strongly support our proposal that CGRP primarily stimulates K+ efflux via activation of K(ATP) channels and thereby induces membrane hyperpolarization in UMR106 cells. Furthermore, our data also suggest that this cascade of initial cellular events may result in rapid changes in cell morphology and decreases in cellular area of the type that are thought to act as triggers for proliferation and/or differentiation in many cellular phenotypes.

Long-latency response to transcranial magnetic stimulation in patients with hemifacial spasm

OBJECTIVE

We studied the long-latency response of the orbicularis oris muscle elicited with transcranial magnetic stimulation in patients with hemifacial spasm (HFS) and evaluated the excitability of the facial nucleus.

METHODS

We compared the thresholds on both sides in 8 normal volunteers and 7 patients with hemifacial spasm. The thresholds were determined as the lowest intensity required to produce motor evoked potentials with an amplitude of at least 50 microV in the orbicularis oris muscle. Average values were given as means +/- standard deviation. Wilcoxon's rank sum test was used for comparisons between the sides of normal subjects and of patients with HFS with respect to the threshold stimulus.

RESULTS

There was no significant difference between the thresholds on the two sides of the normal subjects (mean 1.88+/-5.30%, P > 0.05). In patients with HFS, there was a significant difference between the thresholds on the spasm side and the normal side (mean 20.7+/-13.0%, P < 0.05) In one patient studied after MVD, the difference between both sides disappeared.

CONCLUSION

The difference between the thresholds in patients with HFS and the normalization in threshold after MVD suggested that the mechanism of HFS was hyperexcitability of the facial nucleus.

Periodontal ligament cell culture on the hydrophobic substrate coated with proteins of periodontal ligament fibroblast-conditioned medium

In regenerating periodontal ligament (PDL) around the root of an artificial tooth, an important role is played by some physiologically active substance that promotes adhesion of the cells to the surface of the tooth root and induces cell proliferation and differentiation. In this study, the supernatant of the conditioned medium (CM) of dog periodontal ligament fibroblast (DPLF) was fractionated using an ion exchange chromatography-diethylaminoethyl (IEC-DEAE) column. DPLFs were cultured on hydrophobic dishes coated with each fraction. Cell proliferative activity and alkaline phosphatase (ALPase) activity, including electron microscopic features of the contact surface between the cells and the dish, were investigated. The DPLF-CM was separated by IEC-DEAE column into six fractions. Each fraction promoted an increase in DNA content and ALPase activity of the cultured DPLF, and especially remarkable were fractions 2 and 3. Fraction 2 at a molecular weight (Mw) of 210, 160, 85, 50 and 22 kD, and fraction 3 at Mw = 21 and 23 kD contained the type of proteins not found in other fractions. Electron microscopic analysis revealed that the cells in the coating group were in close contact with the surface of the dishes and that fine fibers protruding from the cell membrane clinged to the dishes. In the control group, a wide gap between the cells and the dishes was observed. These findings suggest that the DPLF-CM fractions contain specific physiological activating factors that induce proliferation and differentiation as well as cell adhesion of the DPLF cells.

Transcranial magnetic stimulation of the oculomotor and abducens nerves: determining the site of excitation in the cat

The authors have attempted to stimulate the feline oculomotor and abducens nerves using a magnetic coil (MC) and to determine the optimal reliable MC position for eliciting motor evoked potentials. The authors have also determined the site of excitation to analyze the validity and potential advantages of this technique as a means of neurophysiologically studying the oculomotor and abducens nerves. The potentials of both of these muscles are evoked by MC placed to be symmetrical to the line connecting the vertex and the center of the eyeball on the side being examined, as the coil center corresponds to the midpoint of this line. The latencies of the motor responses of the superior rectus and lateral rectus were 1.08 +/- 0.22 and 1.02 +/- 0.21 msec, respectively, suggesting that magnetic stimulation excites both the oculomotor and the abducens nerve at the superior orbital fissure.

Up-regulation of inducible nitric oxide (NO) synthase and NO production in HL-60 cells stimulated to differentiate by phorbol 12-myristate 13-acetate plus 1,25-dihydroxyvitamin D3 is not obtained with dimethylsulfoxide plus 1,25-dihydroxyvitamin D3

In previous studies we found that the calciotropic hormone 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] augments the action of either prostaglandin E1 (PGE1) or NaF to induce differentiation of human promyelocytic HL-60 cells, a process that features increased generation of nitric oxide (NO) via up-regulation of inducible nitric oxide synthase (iNOS). We have now examined the short-term interaction of 1,25(OH)2D3 with phorbol 12-myristate 13-acetate (PMA) and dimethylsulfoxide (DMSO) in these cells. PMA (100 nM) alone generally up-regulated several classical indices of macrophagic differentiation and stimulated cellular production of interleukin (IL)-1alpha, IL-6, tumor-necrosis factor (TNF)-alpha, PGE2, and NO. Increased generation of NO primarily resulted from increased expression of cellular iNOS. When 1,25(OH)2D3 (10 nM) was added to PMA treatments, most PMA-induced changes, particularly its effects to up-regulate iNOS-dependent NO production and change cell morphology, were multiplicatively augmented. In contrast, DMSO (1.3%) alone, an inducer of granulocytic differentiation, increased cytokine production, but failed to stimulate NO production or induce iNOS. In contrast to its striking interaction with PMA, 1,25(OH)2D3 could not augment DMSO's differentiative effects. Changes in cellular cytokine production were eliminated as the driving force in HL-60 differentiation when specific neutralizing antibodies failed to produce any attenuation of iNOS up-regulation or of the shifts in cell morphology. However, indomethacin (30 microM) blocked the synergistic interaction between 1,25(OH)2D3 + PMA to shift cell morphology and stimulate NO production. Subsequently adding PGE2 (1 ng/ml) to indomethacin-treated cells restored the ability of 1, 25(OH)2D3 + PMA to interactively increase cellular NO production, but failed to fully replicate the strong shift in cell morphology typical of PMA + 1,25(OH)2D3 treatments. Our findings suggest that interaction between 1,25(OH)2D3 and PMA to induce macrophagic differentiation increases iNOS-dependent NO production by a mechanism involving a cyclooxygenase product(s), possibly PGE2.

The acoustic reflex for filtered broadband stimuli: a lesser contribution of the lower frequency neurons

The effects of the cut-off frequency of the filtered broadband stimuli on the human acoustic reflex (AR) were examined to observe the relation between the area of excitation in the cochlea and the AR response. The results obtained have indicated that all the input from the cochlear region does not equally contribute to trigger the AR equally; i.e., there is a lesser contribution from the frequency region below 700 Hz.

Expression of the neural cell adhesion molecule in astrocytic tumors: an inverse correlation with malignancy

BACKGROUND

Cell adhesion molecules are among the key factors in the development of the malignant potential of brain tumors. The aim of this study was to investigate the expression of the neural cell adhesion molecule (NCAM) in human astrocytic tumors and assess any relationship between NCAM expression and the degree of malignancy.

METHODS

The expression of NCAM was examined in 52 astrocytic tumors by Western blot analysis. From them the authors selected 23 adult supratentorial ordinary astrocytic tumors and performed quantitative Western blot analysis for each isoform (NCAM 172-180, NCAM 145, NCAM 125-130) to investigate any correlation between the expression of each NCAM isoform and the histologic and biologic malignancy (histology, proliferating cell indices [PCIs] determined by MIB-1 immunohistochemistry, and manifestation on magnetic resonance images [MRIs]). Immunohistochemistry with antihuman NCAM monoclonal antibody was also performed on the tumors from which cryostat sections were available.

RESULTS

Most of the astrocytomas and anaplastic astrocytomas revealed 3 bands at 180, 145, and 125-130kD, whereas in glioblastomas the bands tended to diminish. The expression of each NCAM isoform in astrocytic tumors decreased in proportion to the progression of the histologic malignancy, and the results were also corroborated by immunohistochemical evaluation. An inverse correlation was also observed between the amount of NCAM expression and MIB-1 PCIs. NCAM expression was hardly detectable in those tumors with highly invasive manifestation on MRIs.

CONCLUSIONS

To the authors' knowledge, this study provides the first direct evidence that NCAM is down-regulated in the development of the malignancy of astrocytic tumors; and it is suggested that reduced NCAM expression might be involved in the development of biologic malignancy.

Acoustic reflex threshold and loudness in patients with unilateral hearing losses

The relationship between the acoustic reflex threshold (ART) and loudness was examined in patients with unilateral hearing losses and subjects with simulated hearing losses using a masking method. Significant differences in the ART between the two ears of patients with unilateral hearing losses were correlated with differences in loudness at the level of the ART with differences in loudness determined by the alternate binaural loudness balance test. A similar relationship of ART and the sensation of loudness was also observed in ears with simulated hearing losses. The results obtained in the present study suggest a positive relationship between the ART and loudness, and provide some support for the assumption that a common neuronal information pathway plays an important role both in producing the loudness and eliciting the acoustic reflex.

Expression of the neural cell adhesion molecule in astrocytic tumors: an inverse correlation with malignancy

BACKGROUND

Cell adhesion molecules are among the key factors in the development of the malignant potential of brain tumors. The aim of this study was to investigate the expression of the neural cell adhesion molecule (NCAM) in human astrocytic tumors and assess any relationship between NCAM expression and the degree of malignancy.

METHODS

The expression of NCAM was examined in 52 astrocytic tumors by Western blot analysis. From them the authors selected 23 adult supratentorial ordinary astrocytic tumors and performed quantitative Western blot analysis for each isoform (NCAM 172-180, NCAM 145, NCAM 125-130) to investigate any correlation between the expression of each NCAM isoform and the histologic and biologic malignancy (histology, proliferating cell indices [PCIs] determined by MIB-1 immunohistochemistry, and manifestation on magnetic resonance images [MRIs]). Immunohistochemistry with antihuman NCAM monoclonal antibody was also performed on the tumors from which cryostat sections were available.

RESULTS

Most of the astrocytomas and anaplastic astrocytomas revealed 3 bands at 180, 145, and 125-130kD, whereas in glioblastomas the bands tended to diminish. The expression of each NCAM isoform in astrocytic tumors decreased in proportion to the progression of the histologic malignancy, and the results were also corroborated by immunohistochemical evaluation. An inverse correlation was also observed between the amount of NCAM expression and MIB-1 PCIs. NCAM expression was hardly detectable in those tumors with highly invasive manifestation on MRIs.

CONCLUSIONS

To the authors' knowledge, this study provides the first direct evidence that NCAM is down-regulated in the development of the malignancy of astrocytic tumors; and it is suggested that reduced NCAM expression might be involved in the development of biologic malignancy.

Plasma cell granuloma extending from the extracranial to the intracranial space associated with Epstein-Barr virus infection

A 70-year-old male presented with a plasma cell granuloma extending from the extracranial to the intracranial space. Findings of preoperative magnetic resonance imaging and intraoperative observation indicated that the lesion extended from the temporal muscle to the subarachnoid space, penetrating the frontal bone. The subarachnoid lesion was composed of neutrophils indicating the presence of acute or subacute inflammation. The final diagnosis of the resected tumor was plasma cell granuloma. High levels of antibodies against Epstein-Barr (EB) virus in the cerebrospinal fluid and the immunohistochemical demonstration of EB nuclear antigens in the plasma cell granuloma suggested that EB virus infection was associated with the development of plasma cell granuloma in this patient.

Immunohistochemical examination of c-Met protein expression in astrocytic tumors

Hepatocyte growth factor/scatter factor (HGF/SF), which has various physiological functions, and its receptor c-Met, the human c-met proto-oncogene product, are thought to be determinant in the pathological processes of various malignancies. To investigate the possible role of HGF/SF in the progression of development of astrocytic tumors, we examined the expression of c-Met in these tumors. Immunohistochemistry using the streptavidin-biotin peroxidase complex method and immunofluorescence double staining with anti-c-Met polyclonal and anti-glial fibrillary acidic protein monoclonal antibodies were performed. Positive c-Met expression was detected in 31 of the 42 astrocytic tumors and some of the control cases analyzed. c-Met-positive cells showed morphological characteristics of astrocytes. Especially in the cases of high-grade tumors, c-Met positivity was abundant in cells in both vascular-rich and peripheral regions of the tumors but not in the cells with distinctly malignant features. Immunofluorescence double staining revealed that the c-Met-positive cells were in part of astrocytic origin. We suggest that c-Met-positive cells are affected by some factors in the lesions where the pathological processes are in a state of development. Our studies indicated that c-Met expression might take part in glioma invasion but not in the development of malignancy.

[Is medical linac suitable for high-precision stereotactic irradiation?: investigations in geometrical accuracies of gantry and couch]

Linac-based radiosurgery has many advantages over the gamma knife, including low initial cost and no need of source replacement. On the other hand, most of the medical linacs currently in use were not originally designed to be applied for radiosurgery, and, therefore, careful quality assurance programs are required. In the gantry-head of a linac, a small CCD video camera is mounted in a position optically identical to that of the x-ray source. The video signal from the camera was digitalized to be evaluated for geometrical errors. A metal ball fixed to the stereotactic base frame via XYZ-sliding rods was used as a simulated target. Displacements of the target from the isocenter were measured during rotation of the gantry. Displacements in the gantry-rotation plane were satisfactorily small, while those perpendicular to it were maximal at gantry position angles of 0 degree and 180 degrees. This error night be caused by gravitational vending of the heavy gantry head. Although other major errors of the linac were within one millimeter, the center of coach rotation around the isocenter did not coincide with the center of gantry rotation, probably owing to gravitational vending. Special care should be taken when very small collimators are employed.

Correlation between MIB-1 staining indices and recurrence in low-grade astrocytomas

Although low-grade astrocytomas are histologically benign, some of them recur frequently. We retrospectively investigated the relationship between MIB-1 staining index (SI) and recurrence in 47 low-grade astrocytomas that were treated in Keio University Hospital from 1981 to 1991. We found a correlation between SI and recurrence. MIB-1 SIs recurrent low-grade astrocytomas have been shown to be almost similar to those of astrocytoma grade 3. We concluded that it was very important to examine MIB-1 SI in all astrocytomas especially in low-grade astrocytomas, because MIB-1 SI is one of the factors from which we could predict-recurrence and decide whether radiotherapy or chemotherapy should be performed.

Endoscopic papillary balloon dilation for the management of common bile duct stones: experience of 226 cases

BACKGROUND AND STUDY AIMS

Endoscopic sphincterotomy is a widely accepted technique for the treatment of patients with common bile duct stones. However, it is still associated with occasional complications. The recently developed technique of endoscopic papillary balloon dilation seems to be a safe and effective procedure, and to have great potential for replacing endoscopic sphincterotomy. However, few reports have been published on the use of this technique for bile duct stones. The present study was undertaken to evaluate its safety and efficacy.

PATIENTS AND METHODS

Endoscopic papillary balloon dilation was used to remove common bile duct stones in 226 consecutive patients including 41 patients of ASA classification III/IV, 41 elderly patients (> 80 years) 24 with liver cirrhosis, and 86 with periampullary diverticulum. After dilation of the papilla with a balloon diameter of 8 mm, the stones were retrieved.

RESULTS

In conjunction with the use of a mechanical or/and electrohydraulic lithotriptor in 79 patients (35%) with large stones (> 10 mm in diameter), clearance of the common bile duct was achieved in 225 of 226 patients (99%) without serious complications, such as hemorrhage or severe pancreatitis; mild (n = 13) or moderate (n = 2) pancreatitis occurred in 7% of cases.

CONCLUSIONS

Endoscopic papillary balloon dilation is a safe and effective technique for the treatment of common bile duct stones, even in high-risk patients.

Generation of far field potentials from the trigeminal nerve in the cat

This study provides evidence that far field potentials (FFPs) are generated from the trigeminal nerve in the cat. By stimulating the main mental nerve, three components (component 1, 0.59 +/- 0.06 ms; component 2, 0.81 +/- 0.06 ms; and component 3, 0.98 +/- 0.07 ms) were identified from surface electrodes. These three components were thought to be positive and negative FFPs because each component had a stationary peak and was distributed on the head being divided into positive and negative fields. Results of a study of lesions and recording compound action potentials (CAPs) defined the neural origins of those potentials as follows: component 1, the mandibular nerve at the mandibular foramen; component 2, the mandibular nerve at the foramen ovale; and component 3, somewhere between the gasserian ganglion and the trigeminal root. The amplitude of component 2 decreased when the mandibular nerve at the foramen ovale was immersed in cerebrospinal fluid (CSF) after opening the foramen and recovered to the prior level after closing the foramen with beeswax. We concluded that this transformation resulted in the change in electrical resistance of the volume conductor around the nerve.

Multiple isoforms of neuregulin are expressed in developing rat dorsal root ganglia

Accumulating evidence suggests that neuregulin (NRG) plays special roles in the development of the mammalian nervous system. We have already identified NRG as a survival factor for Schwann cells during development. In this report, we have studied all possible NRG isoforms and expression of NRG in the developing rat dorsal root ganglia (DRG) and compared them with those of brain and spinal cord. Neural NRG isoforms comprise common immunoglobulin and epidermal growth factor domains. Various different transcripts were characterized, which arose by alternative splicing in several regions: N-terminal (exon 1 or 2), spacer (exon 5), juxtamembrane (exon 9 or 10), and cytoplasmic (exon 12, 13, or 14) domains. At least 13 novel isoforms among 16 splice variants were identified. The transmembrane isoforms of NRG are dominant forms in developing rat DRG. The mRNA expression of NRG isoforms in DRG is similar to that in spinal cord, while in brain the expression is much less. The mRNA in DRG was found at similar levels from birth to postnatal day 7 of the premyelinating stage, and it decreased afterward. Our results suggest that several NRGs, including isoforms not reported before, play a role as survival factors for Schwann cells in the premyelinating stage.

Prediction of consistency of meningiomas with preoperative magnetic resonance imaging

BACKGROUND

The consistency of a meningioma is one of the important factors in determining the surgical outcome. If the surgeon is aware of the consistency of a meningioma preoperatively, the surgical plans will be influenced. A few papers have described the correlation between consistency of meningiomas and their magnetic resonance imaging (MRI) findings. However, prediction of consistency with MRI is still difficult. We have tried to predict the consistency of meningiomas with MRI findings more precisely.

METHODS AND RESULTS

Fifty patients diagnosed as having intracranial meningiomas were studied with 1.5 Tesla MRI. We compared the MRI findings with tumor consistency. The intensities of the tumors were categorized into three grades (low, iso, and high) compared to that of the gray matter. T1-weighted images had no specifics, but T2-weighted images and proton density images were useful for the prediction of tumor consistency. Hyperintensity on protein density (PD) and T2-weighted images was a sign of a soft tumor.

CONCLUSION

We presume that T2 and PD are useful for predicting consistency of meningiomas, and their water content is one of the main factors in their consistency. Histology may be one of the factors helpful in defining the consistency of a tumor. In this series, we found no relationship between histology and MRI findings, nor between histology and consistency. If the meningioma is believed to be hard, preoperative endovascular embolization is beneficial, which will induce necrosis of the meningioma and make it soft enough to be removed more easily and safety.