Measurement of laryngeal elevation time using a flexible surface stretch sensor.

BACKGROUND: Dysphagia is a growing health problem in aging societies. An observational cohort study targeting community-dwelling populations revealed that 16% of elderly subjects present with dysphagia. There is a need in elderly communities for systematic dysphagia assessment. OBJECTIVE: This study aimed to verify whether laryngeal elevation in the pharyngeal phase could be measured from the body surface using thin and flexible stretch sensors. METHODS: Thirty-two elderly subjects (17 males, 15 females; mean age ± SD: 89.2 ± 6.2 years) with suspected dysphagia underwent a swallowing contrast examination in which seven stretch sensors were attached to the front of the neck. The elongation of the sensors was measured and compared to the laryngeal elevation time values obtained using videofluorography. The sensor signal detected the laryngeal elevation start time, conclusion of the descent of the larynx, and the laryngeal elevation time. The respective laryngeal elevation times obtained using videofluorography and using the sensor were compared using the Bland-Altman method. RESULTS: The laryngeal elevation time was 1.34 ± 0.46 s with the stretch sensor and 1.49 ± 0.56 s with videofluorography. There was a significant positive correlation between the duration obtained by both methods (r = .69, P < .0001). A negative additional significant bias of -0.15 s (95% confidence interval -0.30 to -0.03, P = .046) was noted in the laryngeal elevation time from the videofluorography measurement. CONCLUSION: Laryngeal elevation time can be measured non-invasively from the neck surface using stretch sensors.

α-Synuclein accumulation reduces GABAergic inhibitory transmission in a model of multiple system atrophy.

Multiple system atrophy is a neurodegenerative disease caused by abnormal α-synuclein (α-syn) accumulation in oligodendrocytes and neurons. We previously demonstrated that transgenic (Tg) mice that selectively overexpressed human α-syn in oligodendrocytes exhibited neuronal α-syn accumulation. Microtubule ß-III tubulin binds to endogenous neuronal α-syn to form an insoluble complex, leading to progressive neuronal degeneration. α-Syn accumulation is increased in the presynaptic terminals of Tg mice neurons and may reduce neurotransmitter release. To clarify the mechanisms underlying its involvement in neuronal dysfunction, in the present study, we investigated the effects of neuronal α-syn accumulation on synaptic function in Tg mice. Using whole-cell patch-clamp recording, we found that the frequency of miniature inhibitory postsynaptic currents was reduced in Tg mice. Furthermore, a microtubule depolymerizing agent restored normal frequencies of miniature inhibitory postsynaptic currents in Tg mice. These findings suggest that α-syn and ß-III tubulin protein complex plays roles for regulation of synaptic vesicle release in GABAergic interneurons, and it causes to reduce GABAergic inhibitory transmission.

Binding of neuronal α-synuclein to ß-III tubulin and accumulation in a model of multiple system atrophy.

Multiple system atrophy (MSA) is a neurodegenerative disease caused by α-synuclein (α-syn) accumulation in oligodendrocytes and neurons. We generated a transgenic (Tg) mouse model in which human α-syn was overexpressed in oligodendrocytes. Our previous studies have revealed that oligodendrocytic α-syn inclusions induced neuronal α-syn accumulation, thereby resulting in progressive neuronal degeneration in mice. We also demonstrated that an insoluble complex of α-syn and ß-III tubulin in microtubules progressively accumulated in neurons, thereby leading to neuronal degeneration. In the present study, we demonstrated that neuronal accumulation of the insoluble complex was derived from binding of α-syn to ß-III tubulin and not from α-syn self-aggregation. Thus, interaction between α-syn and ß-III tubulin plays an important role in neuronal α-syn accumulation in an MSA mouse model.

Proteolytic processing regulates pathological accumulation in dentatorubral-pallidoluysian atrophy.

Dentatorubral-pallidoluysian atrophy is caused by polyglutamine (polyQ) expansion in atrophin-1 (ATN1). Recent studies have shown that nuclear accumulation of ATN1 and cleaved fragments with expanded polyQ is the pathological process underlying neurodegeneration in dentatorubral-pallidoluysian atrophy. However, the mechanism underlying the proteolytic processing of ATN1 remains unclear. In the present study, we examined the proteolytic processing of ATN1 aiming to understand the mechanisms of ATN1 accumulation with polyQ expansion. Using COS-7 and Neuro2a cells that express the ATN1 gene, in which ATN1 was accumulated by increasing the number of polyQs, we identified a novel C-terminal fragment containing a polyQ tract. The mutant C-terminal fragment with expanded polyQ selectively accumulated in the cells, and this was also demonstrated in the brain tissues of patients with dentatorubral-pallidoluysian atrophy. Immunocytochemical and biochemical studies revealed that full-length ATN1 and C-terminal fragments displayed individual localization. The mutant C-terminal fragment was preferentially found in the cytoplasmic membrane/organelle and insoluble fractions. Accordingly, it is assumed that the proteolytic processing of ATN1 regulates the localization of C-terminal fragments. Accumulation of the C-terminal fragment was enhanced by inhibition of caspases in the cytoplasm of COS-7 cells. Collectively, these results suggest that the C-terminal fragment plays a principal role in the pathological accumulation of ATN1 in dentatorubral-pallidoluysian atrophy.

Microtubule depolymerization suppresses alpha-synuclein accumulation in a mouse model of multiple system atrophy.

Multiple system atrophy (MSA) is a neurodegenerative disease caused by an accumulation of alpha-synuclein (alpha-syn) in oligodendrocytes. Little is known about the cellular mechanisms by which alpha-syn accumulation causes neuronal degeneration in MSA. Our previous research, however, revealed that in a mouse model of MSA, oligodendrocytic inclusions of alpha-syn induced neuronal accumulation of alpha-syn, as well as progressive neuronal degeneration. Here we identify the mechanisms that underlie neuronal accumulation of alpha-syn in a mouse MSA model. We found that the alpha-syn protein binds to beta-III tubulin in microtubules to form an insoluble complex. The insoluble alpha-syn complex progressively accumulates in neurons and leads to neuronal dysfunction. Furthermore, we demonstrated that the neuronal accumulation of insoluble alpha-syn is suppressed by treatment with a microtubule depolymerizing agent. The underlying pathological process appeared to also be inhibited by this treatment, providing promise for future therapeutic approaches.

Relationship of experience and the place of work to the level of competency among public health nurses in Japan.

AIM: To examine the actual competencies of public health nurses (PHNs) working in public organizations in Japan in order to clarify the relationship between the level of competency and the number of years of experience and the place of work. METHODS: The subjects were 1799 full-time PHNs working at 135 prefectural public health centers and 115 municipal health centers, which were randomly selected. Each subject received a questionnaire in the mail, requesting basic personal information and a self-evaluation of six levels of achievement in 11 topics in five categories of competencies. RESULTS: The number of respondents was 1261 (70.1%), with a total of 1184 valid responses (65.8%). In terms of the level of competency, the average score was >3 for all items and the number of PHNs who achieved Ladders 5 and 6 was low, with very few achieving Ladder 6, despite having more years of experience. Furthermore, the level of achievement depended on the workplace, position, and academic background. CONCLUSION: The tasks regarding the education of PHNs in Japan are to establish achievement goals clearly and incrementally and to develop methods and systems that consistently and systematically increase competencies, not only in basic undergraduate education, but also for employed PHNs, through specialized education. In particular, educational methods that lead to high-quality experiences need to be selected in order to develop competencies.

Diminished neuronal activity increases neuron-neuron connectivity underlying silent synapse formation and the rapid conversion of silent to functional synapses.

Neuronal activity regulates the synaptic strength of neuronal networks. However, it is still unclear how diminished activity changes connection patterns in neuronal circuits. To address this issue, we analyzed neuronal connectivity and relevant mechanisms using hippocampal cultures in which developmental synaptogenesis had occurred. We show that diminution of network activity in mature neuronal circuit promotes reorganization of neuronal circuits via NR2B subunit-containing NMDA-type glutamate receptors (NR2B-NMDARs), which mediate silent synapse formation. Simultaneous double whole-cell recordings revealed that diminishing neuronal circuit activity for 48 h increased the number of synaptically connected neuron pairs with both silent and functional synapses. This increase was accompanied by the specific expression of NR2B-NMDARs at synaptic sites. Analysis of miniature EPSCs (mEPSCs) showed that the frequency of NMDAR-mediated, but not AMPAR-mediated, mEPSCs increased, indicating that diminished neuronal activity promotes silent synapse formation via the surface delivering NR2B-NMDARs in mature neurons. After activation of neuronal circuit by releasing from TTX blockade (referred as circuit reactivation), the frequency of AMPAR-mediated mEPSCs increased instead, and this increase was prevented by ifenprodil. The circuit reactivation also caused an increased colocalization of glutamate receptor 1-specfic and synaptic NR2B-specific puncta. These results indicate that the circuit reactivation converts rapidly silent synapses formed during activity suppression to functional synapses. These data may provide a new example of homeostatic circuit plasticity that entails the modulation of neuron-neuron connectivity by synaptic activity.

Re-expression of NR2B-containing NMDA receptors in vitro by suppression of neuronal activity.

N-methyl-D-aspartate receptors (NMDARs) are known to play critical roles in the development of the nervous system, and their expression is regulated in an activity-dependent fashion during development. However, the regulation of NMDAR expression after circuit formation is less well understood. To examine this, we performed patch-clamp recordings from chick cerebral neurons in an activity-controlled culture. Analysis of NMDAR channels from neurons before synapse formation showed that there are two components in channel open kinetics. The major slow component is clearly blocked by ifenprodil, a specific inhibitor of NR2B-containing NMDARs. In contrast, slow component of NMDAR channel opening from neurons after synapse formation became minor and ifenprodil had little effect on the NMDAR channel openings. Furthermore, this change is reversibly regulated by neuronal activity, in that suppression induces the re-expression of NR2B-containing NMDARs, even after circuit formation.