Impact of screening with thyroid ultrasonography in myasthenia gravis patients.

OBJECTIVES: This study was conducted to screen thyroid abnormality evaluated with ultrasonography (US) in patients with myasthenia gravis (MG) and investigate further when malignancy is suspected. METHODS: Thyroid screening using US was conducted in 162 patients with MG. In cases where malignancy was suspected, further investigations were performed. RESULTS: Abnormal US findings were detected in 125 of 162 patients with MG (72 patients with nodules, 74 patients with cysts, 27 patients with diffuse findings such as enlargement, atrophy, a hypoechoic pattern or a heterogenous echoic pattern, and 28 patients with calcification). From among these 125 subjects, 30 patients underwent further examinations such as needle aspiration cytology. As a result, six patients (3.7% of 162 cases) were positive for papillary carcinoma. The size of the carcinoma in three patients was <10 mm, yet the stage of thyroid carcinomas was high (stage III or IVa) in all six cases. CONCLUSIONS: Our data suggest that the prevalence of thyroid carcinoma in cases of MG may be higher than that of the general population. Furthermore, in patients with MG, there is a possibility that the stage of the carcinoma is higher even when the carcinoma is of a very small size. Patients with MG, when diagnosed, should be advised to undergo US screening of the thyroid because most cases of thyroid carcinoma are highly curable.

Loss of polyubiquitin gene Ubb leads to metabolic and sleep abnormalities in mice.

AIMS: Ubiquitin performs essential roles in a myriad of signalling pathways required for cellular function and survival. Recently, we reported that disruption of the stress-inducible ubiquitin-encoding gene Ubb reduces ubiquitin content in the hypothalamus and leads to adult-onset obesity coupled with a loss of arcuate nucleus neurones and disrupted energy homeostasis in mice. Neuropeptides expressed in the hypothalamus control both metabolic and sleep behaviours. In order to demonstrate that the loss of Ubb results in broad hypothalamic abnormalities, we attempted to determine whether metabolic and sleep behaviours were altered in Ubb knockout mice. METHODS: Metabolic rate and energy expenditure were measured in a metabolic chamber, and sleep stage was monitored via electroencephalographic/electromyographic recording. The presence of neurodegeneration and increased reactive gliosis in the hypothalamus were also evaluated. RESULTS: We found that Ubb disruption leads to early-onset reduced activity and metabolic rate. Additionally, we have demonstrated that sleep behaviour is altered and sleep homeostasis is disrupted in Ubb knockout mice. These early metabolic and sleep abnormalities are accompanied by persistent reactive gliosis and the loss of arcuate nucleus neurones, but are independent of neurodegeneration in the lateral hypothalamus. CONCLUSIONS: Ubb knockout mice exhibit phenotypes consistent with hypothalamic dysfunction. Our data also indicate that Ubb is essential for the maintenance of the ubiquitin levels required for proper regulation of metabolic and sleep behaviours in mice.

A recovery from enhancement of activation in auditory cortex of patients with idiopathic sudden sensorineural hearing loss.

OBJECTIVE: We previously reported enhanced activation of auditory cortex in patients with bilateral chronic inner-ear hearing loss. To determine whether this enhancement can exhibit a short-term alteration, we measured auditory evoked magnetic fields (AEFs) in patients with idiopathic sudden sensorineural hearing loss (ISSHL) in the acute phase (AP) and recovery phases (RPs). METHODS: We recorded AEFs in two unilateral ISSHL patients at three time points (AP, RP1, and RP2) using a whole-head neuromagnetometer. Tone bursts of 1 kHz were presented monaurally to the affected and healthy ear at four different intensities (40-70 dB HL). RESULTS: Both patients showed the enhancement of N100 m moment at AP and not at RPs in response to the affected ear stimulation, and stronger N100 m moment in ipsilateral than contralateral hemisphere in response to the healthy ear stimulation at AP. CONCLUSIONS: Enhancement of N100 m amplitude occurs in ISSHL patients and disappears on the scale of days. Enhancement of activity in the auditory cortex derived from inner-ear hearing loss can thus exhibit short-term change. SIGNIFICANCE: The results of this study provide first evidence for a recovery from enhancement of activation in the auditory cortex following injury of peripheral hearing organ.

Purification and characterization of human liver beta-galactosidase from a patient with the adult form of GM1 gangliosidosis and a normal control.

beta-Galactosidases were purified to homogeneity from livers of a normal control and a patient with the adult form of GM1 gangliosidosis. The purification was achieved by chromatography on DEAE-Sepharose fast flow, Con A-Sepharose, p-aminophenyl-1-thio-beta-D-galactopyranoside-Sepharose, and QAE-Mono Q. The normal and mutant enzymes were purified about 5000-fold with a yield of 10% and 1800-fold with a yield of 34%, respectively, and could hydrolyze 4-methylumbelliferyl-beta-D-galactoside, GM1 ganglioside, and asialofetuin. The purified normal enzyme was eluted from a TSK gel G-4000SW column as three symmetrical peaks of protein which were coincident with the three peaks of enzyme activity. The enzyme in these three peaks had apparent molecular weights of 800,000 (polymer), 140,000 (dimer), and 65,000 (monomer), whereas the mutant enzyme was eluted as two symmetrical peaks of protein and enzyme activity. The apparent molecular weight of a major monomeric form of the enzyme (beta-galactosidase A) was 60,000, and no dimeric form of the enzyme existed. Normal and mutant purified enzyme preparations migrated as a single major protein band with apparent molecular weights of 65,000 or 60,000, respectively, by SDS-polyacrylamide gel electrophoresis after treatment with mercaptoethanol. On isoelectric focussing, the mutant enzyme migrated more anodally than the normal enzyme. The mutant enzyme also had altered enzyme properties, such as pH optimum, Km values, substrate specificity and heat-stability. These data on the characteristics of the purified enzyme preparations provide the first direct evidence that patients with the adult form of GM1 gangliosidosis have a structurally altered beta-galactosidase.

CSF hypocretin-1/orexin-A concentrations in patients with subarachnoid hemorrhage (SAH).

The aim of this study was to examine the role of the hypothalamic hypocretin/orexin system in complications of delayed ischemic neuronal deficit (DIND) resulting from symptomatic vasospasm in patients with aneurysmal subarachnoid hemorrhage (SAH). CSF hypocretin-1/orexin-A levels were measured in 15 SAH patients. DIND complications occurred in seven patients with symptomatic vasospasm. Hypocretin-1/orexin-A levels were low in SAH patients during the 10 days following the SAH event. CSF hypocretin-1/orexin-A levels were lower in patients with DIND complications than in those who did not develop DIND. A significant transient decline in CSF hypocretin-1/orexin-A levels was also observed at the onset of DIND in all patients with symptomatic vasospasm. The reduced hypocretin/orexin production observed in SAH patients may reflect reduced brain function due to the decrease in cerebral blood flow. These results, taken together with recent experimental findings in rats that indicate hypocretin receptor 1 (orexin 1 receptor) mRNA and protein are elevated following middle cerebral artery occlusion, suggest that a reduction in hypocretin/orexin production in SAH and DIND patients is associated with alterations in brain hypocretin/orexin signaling in response to ischemia.

CSF hypocretin/orexin levels in narcolepsy and other neurological conditions.

OBJECTIVE: To examine the specificity of low CSF hypocretin-1 levels in narcolepsy and explore the potential role of hypocretins in other neurologic disorders. METHODS: A method to measure hypocretin-1 in 100 microL of crude CSF sample was established and validated. CSF hypocretin-1 was measured in 42 narcolepsy patients (ages 16-70 years), 48 healthy controls (ages 22-77 years,) and 235 patients with various other neurologic conditions (ages 0-85 years). RESULTS: As previously reported, CSF hypocretin-1 levels were undetectably low (<100 pg/mL) in 37 of 42 narcolepsy subjects. Hypocretin-1 levels were detectable in all controls (224-653 pg/mL) and all neurologic patients (117-720 pg/mL), with the exception of three patients with Guillain-Barré syndrome (GBS). Hypocretin-1 was within the control range in most neurologic patients tested, including patients with AD, PD, and MS. Low but detectable levels (100-194 pg/mL) were found in a subset of patients with acute lymphocytic leukemia, intracranial tumors, craniocerebral trauma, CNS infections, and GBS. CONCLUSIONS: Undetectable CSF hypocretin-1 levels are highly specific to narcolepsy and rare cases of GBS. Measuring hypocretin-1 levels in the CSF of patients suspected of narcolepsy is a useful diagnostic procedure. Low hypocretin levels are also observed in a large range of neurologic conditions, most strikingly in subjects with head trauma. These alterations may reflect focal lesions in the hypothalamus, destruction of the blood brain barrier, or transient or chronic hypofunction of the hypothalamus. Future research in this area is needed to establish functional significance.

Influence of unilateral deafness on auditory evoked magnetic field.

To investigate the effect of unilateral deafness on central auditory mechanisms, we examined patients with unilateral deafness of various durations. Auditory evoked magnetic fields (AEF) were recorded using a whole-head neuromagnetometer. In patients who had unilateral deafness for more than 3 weeks, the average N100m latency in the ipsilateral hemisphere did not differ from that in the contralateral hemisphere. In addition, in some patients with congenital or early onset deafness, the equivalent current dipole (ECD) moment was larger in the ipsilateral hemisphere than in the contralateral hemisphere. These findings suggest that unilateral deafness may cause reorganization of the central auditory pathway. They also suggest that central auditory pathway in adults has some plasticity, though not as much as in childhood.

Changes in CSF hypocretin-1 (orexin A) levels in rats across 24 hours and in response to food deprivation.

Hypocretin-1 is consistently detectable in the CSF of healthy human subjects, but is absent in narcoleptics. However, functional roles of CSF hypocretin are largely unknown. We examined fluctuation of CSF hypocretin-1 across 24 h and in response to food restriction in rats. Hypocretin-1 levels were high during the dark period when animals were active, but decreased by 40% toward the end of the light (rest) period. After 72 h food deprivation hypocretin-1 levels during the rest phase increased to concentrations similar to those seen during the baseline active phase; however, no increase in response to food deprivation was observed during the active phase. These results indicate an important link between circadian control of sleep and energy homeostasis via the hypocretin system.

Acute responses of renal nerve activity to microgravity induced by free drop in anesthetized rats.

To examine acute cardiovascular and autonomic responses to microgravity (microG), arterial pressure (AP), aortic flow velocity (AFV), central venous pressure (CVP), and renal nerve activity (RNA) were measured in anesthetized rats during 4.5 s of microG produced by free drop. A smooth and immediate reduction in gravity occurred during free drop, microG being achieved 100 ms after the start of the drop. Acute microG elicited an immediate and striking, but transient, decrease in RNA with no significant change in AP and AFV, but a significant decrease in CVP. The decrease in RNA lasted 2 s, then RNA recovered to the control level despite the G value remaining at < 0.001 for 4.5 s. The RNA decrease was attenuated or completely abolished by sinoaortic denervation, vagotomy, or sinoaortic denervation plus vagotomy. These results suggest that acute microG conditions stimulate sinoaortic and cardiopulmonary mechanoreceptors and suppress RNA.

1-Methyl-4-phenylpyridinum kills differentiated PC12 cells with a concomitant change in protein phosphorylation.

1-Methyl-4-phenylpyridinum (MPP+), a selective neurotoxin, destroys the dopaminergic nigrostriatal pathway and results in a parkinsonian syndrome. Exposure of differentiated PC12 cells with nerve growth factor for 5 days to MPP+ (100 microM) for 4 h induced DNA fragmentation which is typical for the programmed cell death. MPP+ treatment (100 microM) concomitantly stimulates S6 kinase activity and resultant phosphorylation of S6 protein of 40S ribosomal subunits in the cells. Cycloheximide treatment prevents the MPP(+)-induced DNA fragmentation and enhancement of the phosphorylation of S6 protein. The present data demonstrate that neurotoxin, MPP+, kills differentiated PC12 cells by the apparent involvement of apoptotic process. Furthermore, the data strongly suggest that a change in protein phosphorylation might be involved in the signal transduction of MPP+ neurotoxicity and/or the protection from its toxicity.

Enhanced activation of the auditory cortex in patients with inner-ear hearing impairment: a magnetoencephalographic study.

OBJECTIVE: Injury of peripheral auditory organ often induces abnormality of loudness sensation such as loudness recruitment. However, objective evaluation of this phenomenon has rarely been performed. To elucidate this abnormal loudness sensation, cortical mechanisms were investigated by recording auditory evoked magnetic fields (AEFs). METHODS: We recorded AEFs in 8 patients suffering from inner-ear hearing impairment with loudness recruitment and in 14 healthy hearing controls using a 122-channel whole-head neuromagnetometer. Tone bursts of 1 kHz were presented monaurally at 4 different intensities (40, 50, 60, 70 dB HL) with a constant interstimulus interval of 1 s. RESULTS: In both groups, the 100 ms response (N100m) increased in amplitude and decreased in latency as a function of stimulus intensity in both hemispheres. Concerning the source strength, increment of dipole moment of N100m was more rapid according to the stimulus intensity in patients compared with that in healthy subjects. Source strength of N100m was enhanced at high stimulus intensity in patients, and its ratio to healthy subjects was 1.08 at 50 dB, 1.69 at 60 dB and 2.04 at 70 dB. CONCLUSIONS: In patients with inner-ear hearing impairment, enhanced activation of the auditory cortex was observed, and may help explain loudness recruitment.

Functional evidence for involvement of bumetanide-sensitive Na+K+2CI- cotransport in the hepatoportal Na+ receptor of the Sprague-Dawley rat.

To investigate mechanisms involved in hepatoportal Na+ sensing, responses of hepatic afferent nerve activity (HANA) to intraportal hypertonic NaCl injection were measured before, and after, intraportal infusion of inhibitors of Na+ transport systems. HANA increased in response to the intraportal injection of 0.75 M NaCl in a dose-dependent manner. The HANA response was not affected by amiloride or 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS), but was suppressed in a dose-dependent manner by intraportal infusion of ouabain, furosemide, or bumetanide. These results indicate that the hepatoportal Na+ receptor senses the Na+ concentration via the bumetanide-sensitive Na+K+2Cl- cotransporter.

Response of renal sympathetic nerve activity to parabolic flight-induced gravitational change in conscious rats.

The renal sympathetic nerve activity (RNA) response to gravitational changes induced by parabolic flight was examined in chronically instrumented conscious rats. Two types of RNA responses were found. In six out of 12 rats, the RNA did not respond during the 2 G period, but immediately fell to background levels on entry into microgravity (microG), then recovered to the 1 G control level during continued microG (shutdown obvious group). In the other six rats, the RNA increased to 158+/-13% at the end of the 2 G period, increased further to 195+/-22% on entry into microG, then gradually recovered to that seen at 1 G (shutdown obscure group). The mean arterial pressure in the shutdown obvious group was significantly higher and the heart rate tended to be higher than in the shutdown obscure group, suggesting that the baseline sympathetic tone in the shutdown obvious group was higher than in the shutdown obscure group. These results suggest that the RNA response to parabolic flight might be affected by the baseline sympathetic tone.

Acute response of aortic nerve activity to free drop-induced microgravity in anesthetized rats.

To test the hypothesis that arterial baroreflex was stimulated during microgravity (microG), arterial pressure (AP), intrathoracic pressure (ITP), and aortic nerve activity (ANA) were measured in anesthetized rats during 4.5 s of microG produced by free drop. A smooth and immediate reduction in G occurred during free drop, microG being achieved 100 ms after the start of the drop. Acute microG elicited an immediate and striking, but transient, increase in ANA, with no significant change in the AP, but a significant decrease in the end-expiratory ITP. The calculated transmural pressure of the aorta increased by 6.9 mmHg 2 s after the start of the drop. The increase in ANA lasted 2 s, then ANA returned to the control level, despite the calculated end-expiratory transmural pressure still being high. These results suggest that microG conditions stimulate the aortic baroreceptor by increasing transmural pressure by reducing the ITP. However, this effect is only transient, probably due to the high-pass property of the baroreceptors.

Induction of human leukocyte antigen-A,B,C and -DR on cultured human oligodendrocytes and astrocytes by human gamma-interferon.

gamma-Interferon (IFN-gamma) is known to induce expression of major histocompatibility complex (MHC) class II antigens on murine astrocytes and MHC class I antigens on murine oligodendrocytes. We studied whether the human IFN-gamma could induce the expression of Human Leukocyte Antigen (HLA)-A, B, C and -DR antigens on cultured human glia from autopsied brain white matter tissue. HLA-A, B, C antigens were induced on both human astrocytes and oligodendrocytes, whereas HLA-DR antigens were induced only on some astrocytes. From these results, it is suggested that IFN-gamma affects the expression of MHC class I and class II antigens on astrocytes and oligodendrocytes derived from human brain. The relationship between the induction of MHC class I and class II antigens by IFN-gamma and the pathogenesis of multiple sclerosis is discussed.

Infection of human T-lymphotropic virus type I to astrocytes in vitro with induction of the class II major histocompatibility complex.

To clarify the pathogenesis of human T-lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM), we examined whether HTLV-I infects normal human glial cells in vitro with induction of the major histocompatibility complex (HMC) class II antigen by immunofluorescence method. It was found that about 10% of astrocytes were infected with HTLV-I with induction of class II MHC antigen. Fluorescence-conjugated HTLV-I was adsorbed to 10% of astrocytes. On the contrary, there was no class II MHC antigen expression and very few HTLV-I infection on oligodendrocytes. We speculated that in patients with HAM, HTLV-I-specific, MHC class II antigen restricted, activated CD4+ cells could damage the MHC class II antigen + HTLV-I-infected astrocytes, leading to the disturbance of blood-brain barrier and to the destructive lesion in the central nervous system.

Role of the vestibular system in sudden shutdown of renal sympathetic nerve activity during microgravity in rats.

The purpose of this study was to examine the effect of microgravity (muG) on renal sympathetic nerve activity (RNA) in rats. Additionally, we estimated the participation of the vestibular system in the response of RNA to muG. Eight normal Sprague-Dawley (SD) rats and five chemically and bilaterally labyrinthectomied SD rats were used to measure RNA during free-drop examination (4.5-s duration of muG); arterial pressure (AP) and aortic flow velocity (AFV) were additionally monitored. Although AFV showed no particular change, AP tended to decrease during muG in the later phase. Prior to this AP fall-off, RNA was immediately and markedly attenuated by muG. This attenuation was transient and RNA returned to 1G level within the mu;muG condition. Interestingly, this phenomenon remained even in labyrinthectomied rats. In conclusion, cephalad shift of the body fluid by loading of muG may cause cardiopulmonary low-pressure receptor activation and consequent RNA attenuation, but the participation of the vestibulosympathetic reflex in this phenomenon is not obvious.

Decreased brain histamine content in hypocretin/orexin receptor-2 mutated narcoleptic dogs.

A growing amount of evidence suggests that a deficiency in hypocretin/orexin neurotransmission is critically involved in animal and human forms of narcolepsy. Since hypocretin-containing neurons innervate and excite histaminergic tuberomammillary neurons, altered histaminergic neurotransmission may also be involved in narcolepsy. We found a significant decrease in histamine content in the cortex and thalamus, two structures important for histamine-mediated cortical arousal, in Hcrtr-2 mutated narcoleptic Dobermans. In contrast, dopamine and norepinephrine contents in these structures were elevated in narcoleptic animals, a finding consistent with our hypothesis of altered catecholaminergic transmission in these animals. Considering the fact that histamine promotes wakefulness, decreases in histaminergic neurotransmission may also account for the sleep abnormalities in hypocretin-deficient narcolepsy.

Characteristics of DPOAE audiogram in tinnitus patients.

To investigate cochlear activity in tinnitus, the DPOAE (distortion product otoacoustic emission) audiograms (DP-gram) of tinnitus patients were measured. Nine tinnitus patients (15 ears) with normal hearing and 55 tinnitus patients (75 ears) with hearing impairment were included in this study. Significant decreases in DPOAE amplitude over a limited frequency range were observed in 93.3% of the normal hearing tinnitus group and in 96% of the hearing-impaired tinnitus group. The averaged DP-gram of the normal hearing tinnitus group was significantly different from that of the normal subject (repeated-measures ANOVA, P < 0.01). These results imply that tinnitus may be evaluated objectively by DPOAE.

Increased cortical activation during hearing of speech in cochlear implant users.

To investigate the cortical activities while listening to noise and speech in cochlear implant (CI) users, we compared cerebral blood flow in postlingually deafened CI users with that in normal hearing subjects using positron emission tomography. While noise activation in CI users did not significantly differ from that in normal subjects, hearing speech activated more cortical areas in CI users than in normal subjects. A comparison of speech activation in these two groups revealed higher activation in CI users not only in the temporal cortices but also in Broca's area and its right hemisphere homologue, the supplementary motor area and the anterior cingulate gyrus. In postlingually deafened subjects, the hearing of speech coded by CI may be accompanied by increased activation of both the temporal and frontal cortices.