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Microglia modulate cardiorespiratory activities during chronic hypoxia. It has not been clarified whether microglia are involved in the cardiorespiratory responses to acute hypoxia. Here we investigated this issue by comparing cardiorespiratory responses to two levels of acute hypoxia (13% O2 for 4 min and 7% O2 for 5 min) in conscious unrestrained rats before and after systemic injection of minocycline (MINO), an inhibitor of microglia activation. MINO increased blood pressure but not lung ventilation in the control normoxic condition. Acute hypoxia stimulated cardiorespiratory responses in MINO-untreated rats. MINO failed to significantly affect the magnitude of hypoxia-induced blood pressure elevation. In contrast, MINO tended to suppress the ventilatory responses to hypoxia. We conclude that microglia differentially affect cardiorespiratory regulation depending on the level of blood oxygenation. Microglia suppressively contribute to blood pressure regulation in normoxia but help maintain ventilatory augmentation in hypoxia, which underscores the dichotomy of central regulatory pathways for both systems.

As blood oxygenation decreases (hypoxemia), mammals mount cardiorespiratory responses, increasing oxygen to vital organs. The carotid bodies are the primary oxygen chemoreceptors for breathing, but sympathetic-mediated cardiovascular responses to hypoxia persist in their absence, suggesting additional high-fidelity oxygen sensors. We show that spinal thoracic sympathetic preganglionic neurons are excited by hypoxia and silenced by hyperoxia, independent of surrounding astrocytes. These spinal oxygen sensors (SOS) enhance sympatho-respiratory activity induced by CNS asphyxia-like stimuli, suggesting they bestow a life-or-death advantage. Our data suggest the SOS use a mechanism involving neuronal nitric oxide synthase 1 (NOS1) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). We propose NOS1 serves as an oxygen-dependent sink for NADPH in hyperoxia. In hypoxia, NADPH catabolism by NOS1 decreases, increasing availability of NADPH to NOX and launching reactive oxygen species–dependent processes, including transient receptor potential channel activation. Equipped with this mechanism, SOS are likely broadly important for physiological regulation in chronic disease, spinal cord injury, and cardiorespiratory crisis.

In the field of respiratory clinical practice, the importance of measuring carbon dioxide (CO2) concentrations cannot be overemphasized. Within the body, assessment of the arterial partial pressure of CO2 (PaCO2) has been the gold standard for many decades. Non-invasive assessments are usually predicated on the measurement of CO2 concentrations in the air, usually using an infrared analyzer, and these data are clearly important regarding climate changes as well as regulations of air quality in buildings to ascertain adequate ventilation. Measurements of CO2 production with oxygen consumption yield important indices such as the respiratory quotient and estimates of energy expenditure, which may be used for further investigation in the various fields of metabolism, obesity, sleep disorders, and lifestyle-related issues. Measures of PaCO2 are nowadays performed using the Severinghaus electrode in arterial blood or in arterialized capillary blood, while the same electrode system has been modified to enable relatively accurate non-invasive monitoring of the transcutaneous partial pressure of CO2 (PtcCO2). PtcCO2 monitoring during sleep can be helpful for evaluating sleep apnea syndrome, particularly in children. End-tidal PCO2 is inferior to PtcCO2 as far as accuracy, but it provides breath-by-breath estimates of respiratory gas exchange, while PtcCO2 reflects temporal trends in alveolar ventilation. The frequency of monitoring end-tidal PCO2 has markedly increased in light of its multiple applications (e.g., verify endotracheal intubation, anesthesia or mechanical ventilation, exercise testing, respiratory patterning during sleep, etc.).

Obstructive sleep apnea (OSA) patients are at risk for increased blood pressure and carotid intima-media thickness (IMT), with pulmonary hypertension and right-sided heart failure potentially developing as well. Chronic intermittent hypoxia (IH) has been used as an OSA model in animals, but its effects on vascular beds have not been evaluated using objective unbiased tools. Previously published and current experimental data in mice exposed to IH were evaluated for IMT in aorta and pulmonary artery (PA) after IH with or without normoxic recovery using software for meta-analysis, Review Manager 5. Because IMT data reports on PA were extremely scarce, atherosclerotic area percentage from lumen data was also evaluated. IH significantly increased IMT parameters in both aorta and PA as illustrated by Forest plots (P < 0.01), which also confirmed that IMT values after normoxic recovery were within the normal range in both vascular beds. One-sided scarce lower areas in Funnel Plots were seen for both aorta and PA indicating the likelihood of significant publication bias. Forest and Funnel plots, which provide unbiased assessments of published and current data, suggest that IH exposures may induce IMT thickening that may be reversed by normoxic recovery in both aorta and PA. In light of the potential likelihood of publication bias, future studies are needed to confirm or refute the findings. In conclusion, OSA may induce IMT thickening (e.g., aorta and/or PA), but the treatment (e.g., nasal continuous positive airway pressure) will likely lead to improvements in such findings.

Psychological stress activates the hypothalamus, augments the sympathetic nervous output, and elevates blood pressure via excitation of the ventral medullary cardiovascular regions. However, anatomical and functional connectivity from the hypothalamus to the ventral medullary cardiovascular regions has not been fully elucidated. We investigated this issue by tract-tracing and functional imaging in rats. Retrograde tracing revealed the rostral ventrolateral medulla was innervated by neurons in the ipsilateral dorsomedial hypothalamus (DMH). Anterograde tracing showed DMH neurons projected to the ventral medullary cardiovascular regions with axon terminals in contiguity with tyrosine hydroxylase-immunoreactive neurons. By voltage-sensitive dye imaging, dynamics of ventral medullary activation evoked by electrical stimulation of the DMH were analyzed in the diencephalon-lower brainstem-spinal cord preparation of rats. Although the activation of the ventral medulla induced by single pulse stimulation of the DMH was brief, tetanic stimulation caused activation of the DMH sustained into the post-stimulus phase, resulting in delayed recovery. We suggest that prolonged excitation of the DMH, which is triggered by tetanic electrical stimulation and could also be triggered by psychological stress in a real life, induces further prolonged excitation of the medullary cardiovascular networks, and could contribute to the pathological elevation of blood pressure. The connectivity from the DMH to the medullary cardiovascular networks serves as a chronological amplifier of stress-induced sympathetic excitation. This notion will be the anatomical and pathophysiological basis to understand the mechanisms of stress-induced sustained augmentation of sympathetic activity.

Respiratory activities are produced by medullary respiratory rhythm generators and are modulated from various sites in the lower brainstem, and which are then output as motor activities through premotor efferent networks in the brainstem and spinal cord. Over the past few decades, new knowledge has been accumulated on the anatomical and physiological mechanisms underlying the generation and regulation of respiratory rhythm. In this review, we focus on the recent findings and attempt to elucidate the anatomical and functional mechanisms underlying respiratory control in the lower brainstem and spinal cord. Electronic supplementary material The online version of this article (doi:10.1007/s12576-016-0475-y) contains supplementary material, which is available to authorized users.

Hypoxia sensors are essential for regulating local oxygen (O

Summary Hypoxia sensors are essential for regulating local oxygen (O2) homeostasis within the body. This is especially pertinent within the CNS, which is particularly vulnerable to O2 deprivation due to high energetic demand. Here, we reveal hypoxia-monitoring function exerted by astrocytes through an O2-regulated protein trafficking mechanism within the CNS. Strikingly, cultured mouse astrocytes isolated from the parafacial respiratory group (pFRG) and retrotrapezoid nucleus (RTN) region are capable of rapidly responding to moderate hypoxia via the sensor cation channel transient receptor potential (TRP) A1 but, unlike multimodal sensory neurons, are inert to hyperoxia and other TRPA1 activators (carbon dioxide, electrophiles, and oxidants) in normoxia. Mechanistically, O2 suppresses TRPA1 channel activity by protein internalization via O2-dependent proline hydroxylation and subsequent ubiquitination by an E3 ubiquitin ligase, NEDD4-1 (neural precursor cell-expressed developmentally down-regulated protein 4). Hypoxia inhibits this process and instantly accumulates TRPA1 proteins at the plasma membrane, inducing TRPA1-mediated Ca2+ influx that triggers ATP release from pFRG/RTN astrocytes, potentiating respiratory center activity. Furthermore, astrocyte-specific Trpa1 disruption in a mouse brainstem-spinal cord preparation impedes the amplitude augmentation of the central autonomic respiratory output during hypoxia. Thus, reversible coupling of the TRPA1 channels with O2-dependent protein translocation allows astrocytes to act as acute hypoxia sensors in the medullary respiratory center.

The diaphragm is driven by phrenic motoneurons that are located in the cervical spinal cord. Although the anatomical location of the phrenic nucleus and the function of phrenic motoneurons at a single cellular level have been extensively analyzed, the spatiotemporal dynamics of phrenic motoneuron group activity have not been fully elucidated. In the present study, we analyzed the functional and structural characteristics of respiratory neuron population in the cervical spinal cord at the level of the phrenic nucleus by voltage imaging, together with histological analysis of neuronal and astrocytic distribution in the cervical spinal cord. We found spatially distinct two cellular populations that exhibited synchronized inspiratory activity on the transversely cut plane at C4–C5 levels and on the ventral surface of the mid cervical spinal cord in the isolated brainstem–spinal cord preparation of the neonatal rat. Inspiratory activity of one group emerged in the central portion of the ventral horn that corresponded to the central motor column, and the other appeared in the medial portion of the ventral horn that corresponded to the medial motor column. We identified by retrogradely labeling study that the anatomical distributions of phrenic and scalene motoneurons coincided with optically detected central and medial motor regions, respectively. Furthermore, we anatomically demonstrated closely located features of putative motoneurons, interneurons and astrocytes in these regions. Collectively, we report that phrenic and scalene motoneuron populations show synchronized inspiratory activities with distinct anatomical locations in the mid cervical spinal cord.

BackgroundUsual clinical practice for arterial blood gas analysis (BGA) in conscious patients involves a one-time arterial puncture to be performed after a resting period of 20–30 min. The aim of this study was to evaluate the use of transcutaneous BGA for estimating this gold standard arterial BGA.MethodsSpontaneously breathing Asian adults (healthy volunteers and respiratory patients) were enrolled (n = 295). Transcutaneous PO2(PtcO2) and PCO2(PtcCO2) were monitored using a transcutaneous monitor (TCM4, Radiometer Medical AsP, Denmark) with sensors placed on the chest, forearm, earlobe or forehead. Transcutaneous BGA at 1-min intervals was compared with arterial BGA at 30 min. Reasonable steps to find severe hypercapnia with PaCO2 > 50 mmHg were evaluated.ResultsSensors on the chest and forearm were equally preferred and used because of small biases (n = 272). The average PCO2bias was close to 0 mmHg at 4 min, and was almost constant (4–5 mmHg) with PtcCO2being higher than PaCO2at ≥8 min. The limit of agreement for PCO2narrowed over time: ± 13.6 mmHg at 4 min, ± 7.5 mmHg at 12–13 min, and ± 6.3 mmHg at 30 min. The limit of agreement for PO2also narrowed over time (± 23.1 mmHg at 30 min). Subgroup analyses showed that the PaCO2and PaO2levels, gender, and younger age significantly affected the biases. All hypercapnia subjects with PaCO2 > 50 mmHg (n = 13) showed PtcCO2 ≥ 50 mmHg for until 12 min.ConclusionsAlthough PtcCO2is useful, it cannot completely replace PaCO2because PCO2occasionally showed large bias. On the other hand, the prediction of PaO2using PtcO2was unrealistic in Asian adults. PtcCO2 ≥ 50 mmHg for until 12 min can be used as a screening tool for severe hypercapnia with PaCO2 > 50 mmHg.

Objectives: Recent reports on venous blood gas analysis have shown that venous bicarbonate concentration is useful in the evaluation of the body acid-base status. Most of these reports have been based on the Bland-Altman analysis comparing arterial and venous blood gas values. We intended to elucidate any factors that decrease the agreement between venous and arterial bicarbonate concentrations, which might impair the usefulness of venous blood gas analysis. Methods: Healthy volunteers and patients with various diseases (n = 141) were evaluated by simultaneous arterial and venous blood sampling and Bland-Altman analysis. The venous-arterial bicarbonate concentration difference was compared between healthy volunteers and untreated respiratory alkalosis patients. Intentional hyperventilation (30 or 60 breaths/min, for 3 min) was also performed on 6 healthy volunteers and the venous-arterial bicarbonate concentration difference was evaluated. Results: The relative average bias in bicarbonate concentration was 2.00 mEq/l with venous bicarbonate higher than arterial bicarbonate with 95% limits of agreement of ±4.15 mEq/l. Hyperventilation challenges increased the venous-arterial bicarbonate concentration difference in an intensity-dependent manner. The venous-arterial bicarbonate concentration difference was higher in untreated respiratory alkalosis patients than in healthy volunteers (P Conclusion: Although venous bicarbonate may be useful to evaluate the body acid-base status, hyperventilation increases the venous-arterial bicarbonate concentration difference. Physicians should keep this phenomenon in mind.

Objective: The Japanese drug use system allowed the “once-daily use” of inhaled corticosteroid (ICS) fluticasone furoate (FF) combined with a long acting beta-2 agonist (LABA) vilanterol (VI) against asthma for the first time in 2013. Until then, patients with asthma had to use ICS at least twice-daily. We investigated the real-world efficacy and problems of this drug (FF/VI). Methods: This was an open-label, uncontrolled, within-group time-series (before-after) design. Prior treatments of asthma (twice-daily use of ICS with or without LABA) were switched to once-daily use of FF/VI (200 μg/25 μg). Subjects were evaluated by lung function tests prior to, and 2–3 months after, the initiation of FF/VI. Questions on the asthma control test (ACT) and preference of drugs were asked to patients. Results: One hundred and twenty-eight Japanese asthma outpatients were enrolled from 2014–2018 and 107 subjects completed the study. Peak flow, instantaneous flow at 75% of the forced vital capacity (V75), V50, maximum mid-expiratory flow rate, forced expiratory volume in 1 s, and ACT score in FF/VI-using subjects were significantly increased (all p

otC), is the kernel for respiratory rhythm generation. Despite previous extensive studies focusing on neurons,themechanismofhowrespiratoryrhythmisgeneratedhasnotbeenfullyunderstood. • Here we show that non-neuronal glial cells (a subset of putative astrocytes) in the preB¨ are periodically activated preceding inspiratory neuronal activity, periodic activity of putative astrocytes persists during blockade of neuronal activity, and stimulation of astrocytes in the preB¨ otC induces inspiratory neuronal firings. • These findings together with the previous report that blockade of astrocytic metabolism abolishes inspiratory neural output suggest that astrocytes are functionally involved in respiratory rhythm generation. • These results will help us better understand how respiratory rhythm is generated and how respiratory output is disturbed in various pathological conditions.

Two putative respiratory rhythm generators (RRGs), the para-facial respiratory group (pFRG) and the pre-Botzinger complex (preBotC), have been identified in the neonatal rodent brainstem. To elucidate their functional roles during the neonatal period, we evaluated developmental changes of these RRGs by optical imaging using a voltage-sensitive dye. Optical signals, recorded from the ventral medulla of brainstem-spinal cord preparations of neonatal (P0-P4) rats (n = 44), were analysed by a cross correlation method. With development during the first few postnatal days, the respiratory-related activity in the pFRG reduced and shifted from a preinspiratory (P0-P1) to an inspiratory (P2-P4) pattern, whereas preBotC activity remained unchanged. The mu-opioid agonist [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) augmented preinspiratory activity in the pFRG, while the mu-opioid antagonist naloxone induced changes in spatiotemporal activation profiles that closely mimicked the developmental changes. These results are consistent with the recently proposed hypothesis by Janczewski and Feldman that the pFRG is activated to compensate for the depression of the preBotC by perinatal opiate surge. We conclude that significant reorganization of the respiratory neuronal network, characterized by a reduction of preinspiratory activity in the pFRG, occurs at P1-P2 in rats. The changes in spatiotemporal activation profiles of the pFRG neurones may reflect changes in the mode of coupling of the two respiratory rhythm generators.

Respiratory plasticity contributes to stabilization of ventilation. However, its cellular mechanism has not been clarified. We hypothesized that astrocytes mediate respiratory plasticity, based on ...

Introduction In rheumatoid arthritis (RA) patients receiving immunosuppressive treatments, vaccination against Streptococcus pneumoniae is recommended. The objective of the study was to evaluate the effects of tacrolimus (TAC) on immune response following administration of a 23-valent pneumococcal polysaccharide vaccine (PPSV23) in patients with established RA. Methods Patients with RA (n = 133) were vaccinated with PPSV23. Patients were classified into TAC (n = 29), methotrexate (MTX) (n = 55), control (n = 35), and TAC/MTX (n = 14) treatment groups. We measured the concentrations of pneumococcal serotypes 6B and 23F by using an enzyme-linked immunosorbent assay and determined antibody functionality by using a multiplexed opsonophagocytic killing assay, reported as the opsonization index (OI), before and 4 to 6 weeks after vaccination. A positive antibody response was defined as at least a twofold increase in the IgG concentration or as at least a 10-fold increase in the OI. Results IgG concentrations and OIs were significantly increased in all treatment groups after PPSV23 vaccination. The TAC treatment group appears to respond in a manner similar to that of the RA control group in terms of 6B and 23F serotype concentration and function. In contrast, the MTX group had the lowest immune response. Patients who received a combination of TAC and MTX (TAC/MTX) also had a diminished immune response compared with those who received TAC alone. Conclusions TAC monotherapy does not appear to impair PPSV23 immunogenicity in patients with RA, whereas antibody production and function may be reduced when TAC is used with MTX. Thus, PPSV23 administration during ongoing TAC treatment should be encouraged for infection-prone TAC-treated patients with rheumatic diseases. Trial registration University Hospital Medical Information Network Clinical Trials Registry: UMIN000009566. Registered 12 December 2012. Electronic supplementary material The online version of this article (doi:10.1186/s13075-015-0662-x) contains supplementary material, which is available to authorized users.

The neural mechanisms of propofol-induced central respiratory depression remain poorly understood. In the present study, we studied these mechanisms and the involvement of gamma-aminobutyric acid (GABA)A receptors in propofol-induced central respiratory depression. The brainstem and the cervical spinal cord of 1- to 4-day-old rats were isolated, and preparations were maintained in vitro with oxygenated artificial cerebrospinal fluid. Rhythmic inspiratory burst activity was recorded from the C4 spinal ventral root. The activity of respiratory neurons in the ventrolateral medulla was recorded using a perforated patch-clamp technique. We found that bath-applied propofol decreased C4 inspiratory burst rate, which could be reversed by the administration of a GABAA antagonist, bicuculline. Propofol caused resting membrane potentials to hyperpolarize and suppressed the firing of action potentials in preinspiratory and expiratory neurons. In contrast, propofol had little effect on resting membrane potentials and action potential firing in inspiratory neurons. Our findings suggest that the depressive effects of propofol are, at least in part, mediated by the agonistic action of propofol on GABAA receptors. It is likely that the GABAA receptor-mediated hyperpolarization of preinspiratory neurons serves as the neuronal basis of propofol-induced respiratory depression in the newborn rat.

To study the inflammatory responses of small-airway epithelium in smokers, we harvested enough living epithelial cells (1.97 × 106± 0.74 × 106) with a new ultrathin fiberscope from the very peripheral airways of 22 current smokers and 17 subjects who never smoked after informed consent was obtained. The cells were keratin positive and composed mainly of nonciliated cells. The expression levels of inflammatory markers [interleukin (IL)-8 and intercellular adhesion molecule (ICAM)-1] were evaluated with RT-PCR. The magnitude of the mRNA levels corrected by β-actin transcripts of IL-8 and ICAM-1 was significantly higher in the smokers than in the nonsmokers ( P < 0.001). Furthermore, among current smokers, IL-8 mRNA levels correlated positively with the extent of smoking history [in pack ⋅ years (packs/day × no. of years of smoking); r = 0.754, P < 0.001]. Spontaneously released IL-8 and soluble ICAM-1 levels ( n = 12) from cultured epithelial cells were elevated in subjects with a smoking history than in those without it (IL-8, 1,580 ± 29.6 vs. 354 ± 39.4 pg ⋅ 106cells−1⋅ 24 h−1; P < 0.001; soluble ICAM-1, 356.0 ± 45.9 vs. 112.9 ± 12.9 pg ⋅ 106cells−1⋅ 24 h−1; P < 0.01 by Student's t-test ). In contrast, the epithelial cells from the main bronchi did not show such differences between smokers and nonsmokers. Our study highlighted a close link between smoking and the expression of inflammatory mediators such as IL-8 and ICAM-1 in small airways. Our results also suggested that this new ultrathin bronchofiberscope promised a good approach for the evaluation of cellular changes in the small airways.

Objectives: A meta-analysis suggested that the use of varenicline, which is a partial agonist of nicotinic acetylcholine receptors and is effective in smoking cessation, increases the risk of cardiovascular events within 52 weeks of starting treatment. Defining these events as occurring during drug treatment (usually for 12 weeks) or within 30 days of discontinuation, another meta-analysis showed that the risk was statistically insignificant. In the present study, we aimed to clarify the effect of varenicline-assisted smoking cessation on vascular endothelial function assessed by flow-mediated vasodilation (FMD). Design: Before–after and time-series. Setting: Tochigi Prefecture, Japan. Participants: Data of 85 participants who visited nicotine-dependent outpatient services were reviewed. FMD was repeatedly measured in 33 of the 85 participants. Inclusion criteria: 20 years and older, Brinkman index ≥200, Tobacco Dependence Screener ≥5 and stated motivation to quit smoking. Interventions: Each participant was treated with varenicline titrated up to 1.0 mg twice daily (for 12 weeks in total). Primary and secondary outcome measures: Participants were evaluated by FMD prior to, and 3 months after, complete smoking cessation. Follow-up FMD measurements were carried out every 3 months if possible. Changes in FMD during varenicline use were also evaluated. Results: FMD was significantly increased from 4.0±1.8% to 5.5±2.2% (p

胸部X線所見分類で孤立結節性陰影1例, 多発粟粒状結節性陰影1例, 肺炎様陰影3例の細気管支肺胞上皮癌5例を胸部単純X線写真, X線CTと細気管支鏡所見を対比し検討した. 内視鏡所見は肺炎様陰影を呈した症例では細気管支は漿液性の分泌物が多く肺胞の方から湧き出てくる像がみられ, また, 細気管支に粘膜下主体型の腫瘍および閉塞像が認められた. 散在するポリープ様変化も認められ本症の進展形式を示唆した. 孤立結節性陰影の症例では結節隆起型の腫瘍がみられた. 多発粟粒状結節性陰影の症例では細気管支は全般的に狭窄を起こし粘膜面が蒼白に認められた. 初めて本症を内視鏡で観察することが出来た.

We determined the presence of Ca(2+)/calmodulin-dependent protein kinases (CaMKs), a family of multifunctional proteins engaged in Ca(2+)-linked signaling, in carotid body chemoreceptor cells which are critical for the hypoxia-sensing. Carotid bodies were dissected from anesthetized normoxic adult Wistar rats and were double stained for individual CaMKs and for tyrosine hydroxylase (TH), a marker of chemoreceptor cells. Immunofluorescence was examined by confocal laser scanning microscopy. We found that CaMKI and CaMKII were expressed in chemoreceptor cells, but their distribution and intensity varied. CaMKI immunoreactivity was distributed throughout the cytoplasm, whereas that of CaMKII was localized in the cytoplasmic periphery of chemoreceptor cells. An overlap of CaMKI or CaMKII fluorescent probes with TH affirmed the presence of either protein in the chemoreceptor cells. CaMKIV could not be conclusively visualized by the used method. The study shows the expressions of CaMKI and CaMKII in chemoreceptor cells, which raises the plausibility of CaMKs` role in carotid body function.

The neural inspiratory activity originates from a ventrolateral medullary region called the pre-Bötzinger complex (preBötC), yet the mechanism underlying respiratory rhythmogenesis is not completely understood. Recently, the role of not only neurons but astrocytes in the central respiratory control has attracted considerable attention. Here we report our discovery that an intracellular calcium rise in a subset of putative astrocytes precedes inspiratory neuronal firing in rhythmically active slices. Functional calcium imaging from hundreds of preBötC cells revealed that a subset of putative astrocytes exhibited rhythmic calcium elevations preceding inspiratory neuronal activity with a time lag of approximately 2 s. These preinspiratory putative astrocytes maintained their rhythmic activities even during the blockade of neuronal activity with tetrodotoxin, whereas the rhythm frequency was lowered and the intercellular phases of these rhythms were decoupled. In addition, optogenetic stimulation of preBötC putative astrocytes induced firing of inspiratory neurons. These findings raise the possibility that astrocytes in the preBötC are actively involved in respiratory rhythm generation in rhythmically active slices.

In the statistical analysis of functional brain imaging data, regression analysis and cross correlation analysis between time series data on each grid point have been widely used. The results can be graphically represented as an activation map on an anatomical image, but only activation signal, whose temporal pattern resembles the predefined reference function, can be detected. In the present study, we propose a fusion method comprising innovation approach in time series analysis and statistical test. Autoregressive (AR) models were fitted to time series data of each pixel for the range sufficiently before or after the state transition. Then, the remaining time series data were filtered using these AR parameters to obtain its innovation (filter output). The proposed method could extract brain neural activation as a phase transition of dynamics in the system without employing external information such as the reference function. The activation could be detected as temporal transitions of statistical test values. We evaluated this method by applying to optical imaging data obtained from the mammalian brain and the cardiac sino-atrial node (SAN), and demonstrated that our method can precisely detect spatio-temporal activation profiles in the brain or SAN.

The effect of intravenous recombinant human tissue-type plasminogen activator (tPA) on arterial blood gases was compared with the effect of heparin treatment in acute pulmonary thromboembolism. Fifteen patients received heparin alone (group A), 5 cases were treated with 7.7×106I.U. of tPA (group B) and 10 cases with 15×106I.U. of tPA (group C) combined with heparin treatment. Arterial oxygen tension before treatment was not significantly different among the three groups. PaO2 was dramatically improved on the 1st day in group C. By the 7th day, PaO2 of group B had improved to the level of group C. However, the PaO2 of group A on the 7th day was not significantly different compared to the pre-treatment value. In group C, post-treatment perfusion lung scintigrams were improved compared to the pre-treatment images, but this was not the case in group B. Treatment with tPA is more effective for acute pulmonary thromboembolism than heparin alone and a high dose of tPA (15×106I.U.) leads to rapid improvement in arterial blood gases and lung perfusion images.(Internal Medicine 31: 885-888, 1992)

The sino-atrial node (SAN) is the natural pacemaker of the heart. Mechanisms of the leading pacemaker site generation and dynamic pacemaker shifts in the SAN have been so far studied with an electrophysiological technique, but the detailed spatial distribution of action potential characteristics in the SAN has not been analyzed due to the limited number of simultaneously recorded sites in microelectrode recording. To elucidate the mechanism of leading pacemaker site generation in the SAN, we applied a voltage imaging technique and analyzed the spatial distribution of action potential characteristics in the rabbit SAN. Action potential parameters, i.e., action potential duration at 50% repolarization level, the slope of upstroke, and the slope of the linearly depolarizing early phase of pacemaker activity (phase-4), were calculated from optical signals. Action potential parameter values derived from intracellular recording with a microelectrode and those from optical recording were significantly correlated. The leading pacemaker site occurred in the region of either globally or locally maximum phase-4 slope in 7 of 12 preparations, however, it did not coincide with the region of the early maximum phase-4 slope in the other 5 preparations. Carbenoxolone, a gap junction blocker, changed action potential properties and caused pacemaker shifts. Model simulation, assuming an inhomogeneous distribution of intrinsic properties of SAN cells, reproduced the experimental results. We conclude that the functional structure of the SAN is more inhomogeneous than that dictated by previous models. Besides intrinsic cellular properties, cell-to-cell interaction through gap junctions influences action potential characteristics and leading pacemaker site generation.

Morphine is often used in cancer pain and postoperative analgesic management but induces respiratory depression. Therefore, there is an ongoing search for drug candidates that can antagonize morphine-induced respiratory depression but have no effect on morphine-induced analgesia. Acetylcholine is an excitatory neurotransmitter in central respiratory control and physostigmine antagonizes morphine-induced respiratory depression. However, physostigmine has not been applied in clinical practice because it has a short action time, among other characteristics. We therefore asked whether donepezil (a long-acting acetylcholinesterase inhibitor used in the treatment of Alzheimer's disease) can antagonize morphine-induced respiratory depression. Using the anesthetized rabbit as our model, we measured phrenic nerve discharge as an index of respiratory rate and amplitude. We compared control indices with discharges after the injection of morphine and after the injection of donepezil. Morphine-induced depression of respiratory rate and respiratory amplitude was partly antagonized by donepezil without any effect on blood pressure and end-tidal C0(2). In the other experiment, apneic threshold PaC0(2) was also compared. Morphine increased the phrenic nerve apnea threshold but this was antagonized by donepezil. These findings indicate that systemically administered donepezil partially restores morphine-induced respiratory depression and morphine-deteriorated phrenic nerve apnea threshold in the anesthetized rabbit

Neuromuscular blocking agents suppress central respiratory activity through their inhibitory effects on preinspiratory neurons and the synaptic drive from preinspiratory neurons to inspiratory neurons. Central CO 2 -chemosensitive areas, which partly consist of CO 2 -excited neurons, in the rostral ventrolateral medulla are thought to provide tonic drive to the central respiratory network and involve cholinergic mechanisms, which led us to hypothesize that neuromuscular blocking agents can inhibit CO 2 -excited neurons and attenuate respiratory CO 2 responsiveness. To test this hypothesis, we used isolated brainstem-spinal cord preparations from newborn rats. The increase of C4 burst frequency induced by a hypercapnic superfusate, i.e. respiratory CO 2 responsiveness, was suppressed by the application of neuromuscular blocking agents, either d-tubocurarine (10, 100∝M) or vecuronium (100∝M). These agents (40∝M) also induced hyperpolarization and decreases in firing frequency of CO 2 -excited neurons in the rostral ventrolateral medulla. Our results demonstrate that neuromuscular blocking agents inhibit CO 2 -excited tonic firing neurons and attenuate respiratory CO 2 responsiveness. Key terms: brainstem, chemosensitivity, CO 2 responsiveness, muscle relaxant, nicotinic acetylcholine receptor

We analyzed dynamic processes of neural excitation propagation in the experimentally compressed spinal cord using a high-speed optical recording system. Transverse slices of the juvenile rat cervical spinal cord were stained with a voltage-sensitive dye (di-4-ANEPPS). Two components were identified in the depolarizing optical responses to dorsal root electrical stimulation: a fast component of short duration corresponding to pre-synaptic excitation and a slow component of long duration corresponding to post-synaptic excitation. In the directly compressed dorsal horn, the slow component was attenuated more (attenuated to 37.4 +/- 9.1% of the control) than the fast component (to 70.5 +/- 14.9%) (p < 0.01) at 400 msec after stimulation. Depolarizing optical responses to compression and to chemical synaptic blockade were similar. There was a regional difference between white matter (attenuated to 86.2 +/- 10.5%) and gray matter (to 72.6 +/- 10.4%) (p < 0.03) in compression-induced changes of the fast components; neural activity in the white matter was resistant to compression, especially in the dorsal root entry zone. Depolarizing optical signals in the region adjacent to the directly compressed site were also attenuated; the fast component was attenuated to 77.6 +/- 10.4% and the slow component to 31.8 +/- 11.3% of the control signals (p < 0.01). Spinal cord dysfunction induced by purely mechanical compression without tissue destruction was virtually restored with early decompression. We suggest that a disturbance of synaptic transmission plays an important role in the pathophysiological mechanisms of spinal cord compression, at least under in vitro experimental conditions of juvenile rats.