Yohsuke Hirose

Morphologic characteristics of physiologically defined neurons in the cat trigeminal nucleus principalis

Although the principalis nucleus (Vp) contains trigeminothalamic and internuclear tract cells, the functional and morphologic differences between the two kinds of neurons have remained unsettled. The present study was aimed to address these problems by using the intracellular horseradish peroxidase injection technique in the cat. Of 20 neurons stained, 7 and 13 were located in the dorsomedial subnucleus (Vpd) and ventrolateral subnucleus (Vpv) of Vp, respectively. The Vpd neurons received input from the intraoral structures only but the Vpv neurons from the intraoral or facial structures. Nineteen neurons could be divided as class I and class II, based on the branching pattern of their stem axons. Class I (eight neurons) had an ascending stem axon without branching. Class II was divided into two subclasses (IIa and IIb). Class IIa (eight neurons) had an ascending stem axon from which branches were given off. Their branches formed a local‐circuit restricted to the lower brainstem. Class IIb (three neurons) had a stem axon that formed the local‐circuit only. The dendritic morphology was indistinguishable between different classes of neurons and between the subdivisions. Although the dendritic arborization pattern was governed by the location of the somata, it was suggested to be also important elements for determining primary afferent arborizations. In the brainstem nuclei, the jaw‐closing motor nucleus received the highest density of projections from class II neurons with the receptive field involving the periodontal ligaments. The present study provides new findings that Vp neurons could be divided into three distinct populations and suggests that each population exerts a distinct function with respect to sensory discrimination, sensorimotor reflexes, or both. J. Comp. Neurol. 401:308–328, 1998.

Quantitative ultrastructure of physiologically identified premotoneuron terminals in the trigeminal motor nucleus in the cat

Little is known about the ultrastructure of synaptic boutons contacting trigeminal motoneurons. To address this issue, physiologically identified premotor neurons (n = 5) in the rostrodorsomedial part of the oral nucleus (Vo.r) were labeled by intracellular injections of horseradish peroxidase (HRP) in cats. The ultrastructure of 182 serially sectioned axon terminals from the five neurons was both qualitatively and quantitatively analyzed. In addition, the effects of the glycine antagonist strychnine, GABAA antagonist bicuculline, NMDA antagonist 2‐amino‐5‐phosphonovalerate (APV), and non‐NMDA antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) on Vo.r‐induced postsynaptic potentials in trigeminal motoneurons (n = 11) were examined to evaluate potential signaling substances of the premotor neurons. Labeled boutons made synaptic contacts with either jaw‐closing or ‐opening motoneurons. All the boutons contained pleomorphic vesicles, and most formed a single symmetric synapse either on the somata or on primary dendrites. Morphometric analyses indicated that bouton volume, bouton surface area, apposed surface area, total active zone area, and mitochondrial volume were not different between boutons on jaw‐closing and ‐opening motoneurons. Vesicle number and density, however, were higher for boutons on jaw‐closing motoneurons. The five morphological parameters were positively correlated with bouton volume. Vesicle density was the exception, which tending to be negatively correlated. Intravenous infusion of strychnine or bicuculline suppressed Vo.r‐induced inhibitory postsynaptic potentials (IPSPs) in jaw‐closing motoneurons. Abolition of Vo.r‐induced excitatory postsynaptic potentials in jaw‐opening motoneurons with APV and CNQX unmasked IPSPs. The present results suggest that premotor neurons in the Vo.r are inhibitory and that positive correlations between the ultrastructural parameters associated with synaptic release and bouton size are applicable to the interneurons, as they are in primary afferents. J. Comp. Neurol. 426:13–30, 2000.

Physiologic and morphologic properties of motoneurons and spindle afferents innervating the temporal muscle in the cat.

Little is known about physiology and morphology of motoneurons and spindle afferents innervating the temporalis and on synaptic connections made between the two. The present study was aimed at investigating the above issues at the light microscopic level by using the intracellular recording and horseradish peroxidase or biotinamide labeling techniques and by the use of succinylcholine (SCh) for the classification of spindle afferents in the cat. Temporalis motoneurons had dendritic trees that ranged from a spherical form to an egg‐shaped form. The shape deformation was more prominent for the dendritic trees made by motoneurons located closer to the nuclear border. No axon collaterals of the motoneurons were detected. On the basis of the values for the dynamic index after SCh infusion, temporalis spindle afferents were classified into two populations: presumptive groups Ia and II. The spindle afferents terminated mainly in the supratrigeminal nucleus (Vsup), region h, and the dorsolateral subdivision (Vmo.dl) of the trigeminal motor nucleus (Vmo). The proportion of group Ia afferent terminals was lower in the Vsup than that of group II afferents. In the Vmo.dl, the proportion of group Ia afferent terminals was nearly even throughout the nucleus, but that of group II afferent terminals increased in the more outlying regions. The proportion of terminal distribution in the central region of Vmo.dl was higher for group Ia than group II. The frequency of contacts (presumptive synapses) made by a single spindle afferent on a motoneuron was higher for group Ia than group II. The present study provided evidence that the central organization of spindle afferent neurons is different between groups Ia and II. J. Comp. Neurol. 406:29–50, 1999.

Nasotracheal intubation under curve-tipped suction catheter guidance reduces epistaxis

BackgroundNasotracheal intubation (NTI) has greater potential for trauma of nasopharyngeal mucosa than orotracheal intubation. The present study investigated the success rate of NTI and frequency of nasal bleeding using a curve-tipped suction catheter (CTSC) to guide nasotracheal tube advancement.MethodsSubjects comprised 131 adult patients who underwent NTI. Subjects were randomly divided into two groups: a) NTI under CTSC guidance (G[+] group). The CTSC (14 Fr) was first inserted through the tracheal tube, with the tip of the CTSC emerging from the distal end of the tube. The curved tip was directed ventrally. Both tracheal tube and CTSC were advanced together through the nasopharynx; b) NTI without CTSC guidance (G[-] group). The tracheal tube was advanced into the nasal cavity and passed into the pharynx without CTSC guidance. The time required to pass the endotracheal tube through the nasal cavity (nasal passage time), success rate of nasal passage with nasotracheal tube, and the incidence and severity of nasal bleeding were compared.ResultsSuccess rate for nasal passage was 100% in the G(+) group (62/62) and 82.6% in the G(-) group (57/69; P = 0.0006). Frequency of nasal bleeding was significantly lower in the G(+) group (21/62, 33.9%) than in the G(-) group (37/69, 53.6%; P = 0.023). Severity of nasal bleeding was also significantly lower in the G(+) group than in the G(-) group (P = 0.030).ConclusionsNasotracheal intubation under CTSC guidance increases the success rate of airway instrumentation, and also reduces the incidence and severity of epistaxis.RésuméObjectifĽintubation nasotrachéale (INT) est plus traumatique pour la muqueuse nasopharyngée que ľintubation orale pour la muqueuse oropharyngée. Nous examinons le taux de succès de ľINT et la fréquence ďépistaxis avec ľusage ďun cathéter ďaspiration à extrémité courbée (CAEC) pour guider le placement du tube nasotrachéal.MéthodeLes sujets regroupaient 131 adultes qui ont eu une INT. Ils ont été répartis au hasard en deux groupes: a) INT guidée par un CAEC (groupe G[+]). Le CAEC (14 Fr) a ďabord été inséré au travers du tube trachéal, avec la pointe du CAEC émergeant de ľextrémité distale du tube. La pointe courbée a été dirigée vers le bas. Le tube trachéal et le CAEC ont été poussés ensemble dans le nasopharynx; b) INT sans guide CAEC (groupe G[-]). Le tube trachéal a été avancé dans la cavité nasale et passé dans le pharynx sans guide CAEC. Le temps de passage du tube endotrachéal dans la cavité nasale, le taux de succès du passage nasal avec le tube nasotrachéal et ľincidence et la sévérité de saignements nasaux ont été comparés.RésultatsLe taux de succès du passage nasal a été de 100 % dans le groupe G(+) (62/62) et de 82,6 % dans le groupe G(-) (57/69; P = 0,0006). La fréquence de saignement nasal a été significativement plus faible dans le groupe G(+) (21/62, 33,9 %) que dans le groupe G(-) (37/69, 53,6 %; P = 0,023). La sévérité du saignement nasal a été aussi plus faible dans le groupe G(+), comparé au groupe G(-) (P = 0,030).ConclusionĽintubation nasotrachéale guidée par un CAEC augmente le taux de succès de ľintubation des voies aériennes et réduit ľincidence et la sévérité de ľépistaxis.Objectif Ľintubation nasotracheale (INT) est plus traumatique pour la muqueuse nasopharyngee que ľintubation orale pour la muqueuse oropharyngee. Nous examinons le taux de succes de ľINT et la frequence ďepistaxis avec ľusage ďun catheter ďaspiration a extremite courbee (CAEC) pour guider le placement du tube nasotracheal.

Ľintubation nasotrachéale guidée par un cathéter ďaspiration à extrémité courbée réduit ľépistaxis

BackgroundNasotracheal intubation (NTI) has greater potential for trauma of nasopharyngeal mucosa than orotracheal intubation. The present study investigated the success rate of NTI and frequency of nasal bleeding using a curve-tipped suction catheter (CTSC) to guide nasotracheal tube advancement.MethodsSubjects comprised 131 adult patients who underwent NTI. Subjects were randomly divided into two groups: a) NTI under CTSC guidance (G[+] group). The CTSC (14 Fr) was first inserted through the tracheal tube, with the tip of the CTSC emerging from the distal end of the tube. The curved tip was directed ventrally. Both tracheal tube and CTSC were advanced together through the nasopharynx; b) NTI without CTSC guidance (G[-] group). The tracheal tube was advanced into the nasal cavity and passed into the pharynx without CTSC guidance. The time required to pass the endotracheal tube through the nasal cavity (nasal passage time), success rate of nasal passage with nasotracheal tube, and the incidence and severity of nasal bleeding were compared.ResultsSuccess rate for nasal passage was 100% in the G(+) group (62/62) and 82.6% in the G(-) group (57/69; P = 0.0006). Frequency of nasal bleeding was significantly lower in the G(+) group (21/62, 33.9%) than in the G(-) group (37/69, 53.6%; P = 0.023). Severity of nasal bleeding was also significantly lower in the G(+) group than in the G(-) group (P = 0.030).ConclusionsNasotracheal intubation under CTSC guidance increases the success rate of airway instrumentation, and also reduces the incidence and severity of epistaxis.RésuméObjectifĽintubation nasotrachéale (INT) est plus traumatique pour la muqueuse nasopharyngée que ľintubation orale pour la muqueuse oropharyngée. Nous examinons le taux de succès de ľINT et la fréquence ďépistaxis avec ľusage ďun cathéter ďaspiration à extrémité courbée (CAEC) pour guider le placement du tube nasotrachéal.MéthodeLes sujets regroupaient 131 adultes qui ont eu une INT. Ils ont été répartis au hasard en deux groupes: a) INT guidée par un CAEC (groupe G[+]). Le CAEC (14 Fr) a ďabord été inséré au travers du tube trachéal, avec la pointe du CAEC émergeant de ľextrémité distale du tube. La pointe courbée a été dirigée vers le bas. Le tube trachéal et le CAEC ont été poussés ensemble dans le nasopharynx; b) INT sans guide CAEC (groupe G[-]). Le tube trachéal a été avancé dans la cavité nasale et passé dans le pharynx sans guide CAEC. Le temps de passage du tube endotrachéal dans la cavité nasale, le taux de succès du passage nasal avec le tube nasotrachéal et ľincidence et la sévérité de saignements nasaux ont été comparés.RésultatsLe taux de succès du passage nasal a été de 100 % dans le groupe G(+) (62/62) et de 82,6 % dans le groupe G(-) (57/69; P = 0,0006). La fréquence de saignement nasal a été significativement plus faible dans le groupe G(+) (21/62, 33,9 %) que dans le groupe G(-) (37/69, 53,6 %; P = 0,023). La sévérité du saignement nasal a été aussi plus faible dans le groupe G(+), comparé au groupe G(-) (P = 0,030).ConclusionĽintubation nasotrachéale guidée par un CAEC augmente le taux de succès de ľintubation des voies aériennes et réduit ľincidence et la sévérité de ľépistaxis.Objectif Ľintubation nasotracheale (INT) est plus traumatique pour la muqueuse nasopharyngee que ľintubation orale pour la muqueuse oropharyngee. Nous examinons le taux de succes de ľINT et la frequence ďepistaxis avec ľusage ďun catheter ďaspiration a extremite courbee (CAEC) pour guider le placement du tube nasotracheal.

Quantitative analysis of the dendritic architectures of cat hypoglossal motoneurons stained intracellularly with horseradish peroxidase.

Little is known about the dendritic architecture of cat hypoglossal motoneurons. Thus, the present study was done to provide quantitative descriptions of hypoglossal motoneurons and to determine correlations between dendritic size parameters by using the intracellular horseradish peroxidase (HRP) injection technique in the cat. Twelve hypoglossal motoneurons stained with HRP were antidromically activated by stimulation applied to the medial branch of hypoglossal nerve. Eight (type I) and four (type II) of the 12 motoneurons were located in the ventral and dorsal parts of the ventromedial subnucleus of hypoglossal nucleus, respectively. The somatodendritic morphology of the two types of neurons was remarkably different, especially in the dendritic arborization pattern. The type I neurons established an egg‐shaped dendritic tree that was distributed through the nucleus to the reticular formation; the type II dendritic tree was confined within the nucleus and presented a rostrocaudally oriented, mirror‐image, fan‐shape appearance. The total dendritic area and length and the number of terminations and branch points were significantly larger for type I than for type II neurons. For the two types of neuron, there was a positive correlation between stem dendritic diameter and several dendritic size parameters. Although the slopes of the regression lines were slightly different between the two, these were not statistically significant. The present study provides evidence that hypoglossal motoneurons located in the ventromedial subnucleus could be divided into two types according to the dendritic arborization pattern and quantitative analysis of the dendritic tree and according to neuronal location and suggests that the two types of hypoglossal motoneurons can be viewed as intrinsically distinct cell types: type I and type II, which innervate extrinsic and intrinsic muscles, respectively. In addition, the morphometric analysis made it possible to estimate the size of the dendritic tree by measuring the stem dendritic diameter. J. Comp. Neurol. 405:345–358, 1999.

Influence of acute progressive hypoxia on cardiovascular variability in conscious spontaneously hypertensive rats

The purpose of this study is to examine the influence of acute progressive hypoxia on cardiovascular variability and striatal dopamine (DA) levels in conscious, spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). After preparation for measurement, the inspired oxygen concentration of rats was decreased to 10% within 5 min (descent stage), maintained at 10% for 10 min (fixed stage), and then elevated back to 20% over 5 min (recovery stage). The systolic blood pressure (SBP) and heart rate (HR) variability at each stage was calculated to evaluate the autonomic nervous system response using the wavelet method. Striatal DA during each stage was measured using in vivo microdialysis. We found that SHR showed a more profound hemodynamic response to progressive hypoxia as compared to WKY. Cardiac parasympathetic activity in SHR was significantly inhibited by acute progressive hypoxia during all stages, as shown by the decrease in the high frequency band of HR variability (HR-HF), along with transient increase in sympathetic activity during the early hypoxic phase. This decrease in the HR-HF continued even when SBP was elevated. Striatal DA levels showed the transient similar elevation in both groups. These findings suggest that acute progressive hypoxic stress in SHR inhibits cardiac parasympathetic activity through reduction of baroreceptor reflex sensitivity, with potentially severe deleterious effects on circulation, in particular on HR and circulatory control. Furthermore, it is thought that the influence of acute progressive hypoxia on striatal DA levels is similar in SHR and WKY.

Which nostril should be used for nasotracheal intubation: the right or left? A randomized clinical trial

STUDY OBJECTIVE To determine which nostril is more suitable for nasotracheal intubation in patients with normal patency of both nostrils. DESIGN Prospective, randomized clinical trial. SETTING Operating room of a university medical center. PATIENTS 191 ASA physical status 1 and 2 patients scheduled for elective oral surgery requiring general anesthesia with nasotracheal intubation. INTERVENTIONS Patients were randomized to two groups to undergo nasotracheal intubation through the right nostril (Group R; n = 96) or the left nostril (n = 95). Standard traditional nasotracheal intubation was performed using the Macintosh laryngoscope. Tube rotation was attempted for alignment toward the glottis, and Magill forceps were then used to assist intubation, as necessary. MEASUREMENTS Epistaxis was inspected in the pharynx after the tube tip was passed through the nasal cavity and 15 minutes after nasotracheal intubation was completed. Intubation time was the interval between when the anesthesiologist opened the patients mouth with the cross finger maneuver and when the tube was connected to the anesthetic circuit after nasotracheal completion. MAIN RESULTS The frequency of epistaxis was significantly lower in Group R than Group L (P = 0.0006). Although there was no significant difference in nasal passage time between two groups, the intubation time in Group R (24.5 ± 9.4 sec) was shorter than in Group L (30.5 ± 15.6 sec; P = 0.0015). CONCLUSION Nasal intubation via the right nostril is more safely performed than with the left nostril. Because of less epistaxis and faster intubation.