Biomedical subjects

T Umezaki

Publications and source records attributed to T Umezaki.

At least 19 recordsLinked to original sources

PubMed1999

Cortical influences on the vestibular nuclei of the cat.

Our goal was to study potential substrates for cortical modulation of vestibular reflexes in the cat. In initial experiments, injections of wheat-germ-agglutinate-horseradish-peroxidase into Deiters' nucleus and the rostral descending nucleus revealed bilateral colonies of retrogradely filled neurons in cortical areas 6, 2, and 3a (about 60 cells per colony). In cats anesthetized with chloralose-urethane, we stimulated areas 2 and 3a with trains of pulses while recording from ipsilateral vestibular-nucleus neurons, which were characterized by their responses to sinusoidal tilts and tested for the presence of antidromic responses to stimulation of the upper cervical cord. A majority of the neurons was affected by cortical stimulation, showing either facilitation, inhibition, or a mixture of the two. Stimulation in area 2 was more effective than stimulation in area 3a. Despite the anatomic presence of direct cortico-vestibular projections, properties of facilitation and inhibition suggest that both were evoked by polysynaptic pathways. Cortical effects were broadly distributed to vestibular neurons without regard to responses of these neurons to sinusoidal tilts. There was no significant difference between effects on lateral and medial vestibulospinal tract neurons, but, as a group, vestibulospinal neurons were much more likely to be affected by cortical stimulation than neurons not antidromically activated from the C2 segment. We conclude that, by their influence on vestibulospinal neurons, neurons in cortical areas 2 and 3a should be able to modulate, in behaving animals, vestibular reflexes acting on the neck and limbs.

Animals↗

PubMed1999

Behaviors of bulbar respiratory interneurons during fictive swallowing and vomiting.

Behaviors of the same individual medullary respiratory interneurons were examined during both swallowing and vomiting. In 8 decerebrated and paralyzed cats, 18 neurons having either augmenting expiratory (E-AUG), decrementing expiratory (E-DEC), decrementing inspiratory (I-DEC), or constant inspiratory (I-CON) firing patterns were recorded near the most rostral part of the nucleus ambiguus. All neurons exhibited elementary reflexes to single-shock stimulation of the superior laryngeal nerve. During fictive swallowing elicited by superior laryngeal nerve stimulation, all neurons were basically inactive. During fictive vomiting induced by vagal stimulation and/or emetic drugs, all E-AUG and E-DEC neurons tested either were silent or fired weakly between successive retches, whereas I-DEC and I-CON neurons tested exhibited burst activity during the retching and early-expulsion phases. These results indicate that these bulbar respiratory neurons, which may be involved in respiratory rhythmogenesis, are multifunctional neurons that could also be involved in vomiting but not likely in swallowing.

Animals↗

PubMed1999

Authors' Reply:

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Journal Article↗

PubMed1998

Medullary swallowing-related neurons in the anesthetized cat.

Swallowing-related neurons (SRNs) were recorded systematically in the medulla oblongata of urethane-anesthetized cats. The SRNs received orthodromic inputs from the superior laryngeal nerve (SLN) and showed transient changes in their activity synchronous with swallowing. These neurons could be divided into three types. Type I SRNs are sensory-relay neurons from the SLN in the nucleus of the tractus solitarius (NTS), type II are interneurons located diffusely in the parvocellular reticular formation ventral to the NTS, which received oligosynaptic inputs from the SLN, and type III are motoneurons in the nucleus ambiguus. Some type II neurons still showed the swallowing activity after the animals were paralysed, which suggests that they could be involved in the generation of swallowing outputs.

Anesthetics↗

PubMed1998

Upper airway motor outputs during vomiting versus swallowing in the decerebrate cat.

Swallowing and vomiting are antagonistic motor acts; nevertheless, vomiting can be immediately followed by swallowing. The purpose of this study was to clarify the interrelationship between these two behaviors, particularly in regard to comparing the upper airway motor patterns at the end of the expulsion phase with those during subsequent swallowing. Experiments were conducted using both paralyzed and non-paralyzed decerebrate cats, in which recordings were obtained either from upper airway muscles, the diaphragm and abdominal muscles or from the nerves that innervate those muscles. The activity patterns of most nerves recorded in paralyzed animals were consistent with the behavior recorded in non-paralyzed animals from the muscles innervated by those nerves, with the exception of the cricothyroid and stylopharyngeus muscles. Vomiting can be divided into a series of retches followed by expulsion, which itself can be further subdivided into three phases. The final stage of expulsion, characterized by burst-like exaggerated activity of the laryngeal elevator thyrohyoid and the pharyngeal constrictors, proved to be different from pharyngeal swallowing, as judged from differences in the spatio-temporal patterns of the upper airway motor outputs. However, post-vomiting swallowing activity was still observed even after total deafferentation of the laryngeal and pharyngeal areas in paralyzed animals. It is therefore likely that the central processes for vomiting and swallowing closely relate in generating these two behaviors.

Afferent Pathways↗

PubMed1998

Crossing inputs of the superior laryngeal nerve afferents to medullary swallowing-related neurons in the cat.

To understand the neural mechanism for generation of synchronous activity on both sides during swallowing, we examined the convergence of inputs from the bilateral superior laryngeal nerves (SLNs) in the urethane-anesthetized cat medulla and we also examined the changes in swallowing outputs after a longitudinal brain-stem split in decerebrate cats. Twenty-six (31%) of 84 swallowing-related neurons (SRNs) that were oligosynaptically activated by ipsilateral SLN stimulation and recorded mostly in the reticular formation received contralateral inputs, which were confirmed by orthodromic spike responses (n = 16) or were detected as subliminal facilitatory or inhibitory inputs (n = 10) using conditioning-test stimuli. The rate of convergence of inputs from bilateral SLNs in these SRNs was significantly higher than that (4%) in the SRNs that were regarded as sensory-relay neurons in the nucleus tractus solitarius (NTS). The SRNs receiving signals from the contralateral SLN were located diffusely from the NTS and the adjacent reticular formation to the nucleus ambiguus (NA) and the reticular formation dorso-medial to the NA. A midsagittal split from 3 mm caudal to 6 mm rostral to the obex could change symmetrical swallowing to unilateral swallowing. Thus the crossing projections to the contralateral SRNs appear to contribute to symmetrical swallowing.

Afferent Pathways↗

PubMed1998

Recovery of retching after lesions involving the nucleus of the solitary tract.

The nucleus of the solitary tract (NTS) in the caudal brainstem receives various inputs that trigger vomiting. Chemical (kainic acid) NTS lesions in decerebrate, paralyzed cats temporarily suppressed fictive vomiting induced by different emetics. Subsequently, retching but not expulsion, resumed in 2-3.5 h. Since the NTS does not appear essential for retching, antiemetic drugs targeted at the NTS may not completely suppress vomiting.

Animals↗

PubMed1998

Behaviors of hypoglossal hyoid motoneurons in laryngeal and vestibular reflexes and in deglutition and emesis.

Reflex responses of hypoglossal motoneurons innervating the geniohyoid (GH) and thyrohyoid (TH) muscles from the superior laryngeal (SLN) and vestibular nerves and their behaviors during fictive swallowing and vomiting were examined by recording both the extracellular activities of 11 single cells in the hypoglossal nucleus and GH and TH muscle nerve activity in eight decerebrate, paralyzed, and artificially ventilated cats. The majority of TH motoneurons were either active and/or exhibited shortened antidromic latencies during early expiration. In contrast, GH motoneurons did not exhibit any respiratory-related activity. Electrical single-shock stimulation of the SLN never evoked an excitatory reflex response on GH or TH motoneurons but rather evoked inhibitory responses on the THs. Unlike other hypoglossal motoneurons, GH and TH motoneurons do not appear to receive vestibular inputs. However, they can exhibit robust activities during fictive swallowing and vomiting, particularly during expulsion. Thus these motoneurons may play an important role in airway protection during swallowing and vomiting but not in controlling upper airway patency regulated by vestibular afferents.

Animals↗

PubMed1998

Changes in laryngeal muscle activities during hypercapnia in the cat.

The larynx has three functions: phonation, airway protection, and respiration. Few studies have dealt with laryngeal respiratory function. To elucidate respiratory regulation by the larynx, we studied the changes in the activity of the intrinsic laryngeal muscles during hypercapnia in decerebrated cats. The electromyographic activities of the posterior cricoarytenoid (PCA) and thyroarytenoid (TA) muscles were recorded simultaneously with an electromyogram of the diaphragm, endotracheal pressure, and concentrations of O2 and CO2. The activity of the intrinsic laryngeal muscles during hypercapnia (end-tidal CO2, 8% to 10%) was analyzed in comparison with that during eucapnia. In hypercapnia, both the PCA and TA muscles increased their activities, and the endotracheal pressure during expiration was elevated to a higher level than that in eucapnia. TA muscle activities returned to the level during eucapnia after ligation of the common carotid arteries. These findings suggest that hypercapnia causes a further widening of the glottis during inspiration to decrease inspiratory resistance and a further narrowing of the glottis during expiration to prevent alveolar collapse. Thus it may be concluded that the larynx actively participates in respiratory regulation under the control of the brain stem through a process of peripheral inputs from the carotid receptors.

Airway Resistance↗

PubMed1997

Vestibular inputs to bulbar respiratory interneurons in the cat.

Vestibular inputs to medullary respiratory interneurons were studied in decerebrated and artificially ventilated cats. Extracellular recordings were made from 40 neurons located in the area of pre-Bötzinger complex and activated antidromically from the contralateral ventral respiratory group. Neuronal populations analyzed included inspiratory and expiratory neurons with augmenting, constant and decrementing firing patterns, and a late inspiratory neuron. Seventeen neurons responded to ipsilateral and/or contralateral vestibular nerve electrical stimulation. These responses were observed in all seven cell types. Most neuronal reflex responses consisted of inhibition, while a few consisted of either excitation or a combination of both inhibition and excitation. These results indicate that pre-Bötzinger respiratory interneurons, which may be involved in respiratory rhythmogenesis, also participate in vestibulorespiratory responses.

Animals↗

PubMed1997

Role of nucleus retroambigualis in respiratory reflexes evoked by superior laryngeal and vestibular nerve afferents and in emesis.

An ascending projection from the medullary nucleus retroambigualis (NRA) has recently been described as important for the control of the upper airway during vocalization. We evaluated the importance of this projection in other behaviors by making localized injections of the neurotoxin kainic acid in the NRA in decerebrate cats, most of which were paralyzed and artificially ventilated. In contrast to its importance for vocalization, the NRA is not essential for activation of upper airway musculature during respiration, swallowing, vomiting, or reflexes elicited by superior laryngeal or vestibular nerve afferents. However, kainic acid injections in the NRA and adjacent reticular formation prolonged the inhibitory phrenic motoneuronal response to superior laryngeal nerve stimulation and abolished or reduced abdominal motoneuronal responses during respiration, vomiting, and superior laryngeal nerve stimulation. Thus, of the behaviors we investigated, the importance of the ascending projection from the NRA appears to be limited to vocalization, while descending projections from the NRA region are important in a number of behaviors.

Animals↗

PubMed1997

Role of pre-inspiratory neurons in vestibular and laryngeal reflexes and in swallowing and vomiting.

Fifteen pre-inspiratory (Pre-I) neurons were extracellularly recorded in the pre-Bötzinger complex and their involvements in vestibular (VN) and superior laryngeal (SLN) nerve reflexes and in fictive swallowing and vomiting were tested in decerebrated and artificially ventilated cats. Both type I (1 of 9) and type II (1 of 6) pre-I neurons could project to the contralateral ventral respiratory group region. Pre-I neurons changed their firing during VN and SLN respiratory reflexes and fictive swallowing and vomiting; different response properties were observed among individual pre-I neurons. These results suggest that pre-I neurons are a population of heterogeneous and multi-functional propriobulbar neurons.

Animals↗

PubMed1997

The nucleus retroambigualis controls laryngeal muscle activity during vocalization in the cat.

The purpose of this study was to determine (1) whether the nucleus retroambigualis (NRA) plays an essential role in periaqueductal gray (PAG)-induced vocalization and (2) which NRA neurons are involved in the projection from the PAG to laryngeal motoneurons. Bilateral injections of the neurotoxin kainic acid into the NRA in decerebrate cats abolished PAG-induced vocalization; PAG stimulation after the injections no longer modulated vocal fold adductor or tensor activity, and only tonically, but no longer phasically, activated the abdominal muscles. In contrast, PAG-induced inspiratory excitation remained even after the injections. These results suggest that the NRA is essential for the vocal activation of the laryngeal adductor and abdominal muscles, and that an additional pathway from the PAG to respiratory motoneurons other than through the NRA is important for mediating PAG-induced inspiratory activation. Secondly, axonal projections of NRA neurons to the contralateral nucleus ambiguus (NA) were studied electrophysiologically. Five expiratory neurons, which had decrementing (n=4) or constant (n=1) firing patterns, were identified as both having axonal projections to the NA and receiving inputs from the PAG. Furthermore, following NA stimulation many constant-latency action potentials of silent cells were recorded in the vicinity of the NRA, where many silent cells were also orthodromically activated by PAG stimulation. No NRA augmenting expiratory neurons could be antidromically activated from the NA. It is suggested that the NRA and adjacent reticular formation integrate inputs from the PAG and send outputs to laryngeal motoneurons for vocalization.

Action Potentials↗

PubMed1997

Characteristics of laryngeal receptors analyzed by presynaptic recording from the cat medulla oblongata.

In order to clarify the neural mechanisms for the protective laryngeal reflex, we conducted physiological analysis of laryngeal sensory receptors. In the present study, presynaptic unit activities, which might accurately reflect characteristics of the laryngeal receptor, were recorded with a glass microelectrode in the nucleus of the tractus solitarius of the medulla oblongata in ketamine-urethane anesthetized cats, and the responses to the mechanical and/or chemical stimuli were analyzed. From the results, it was demonstrated that highly sensitive mechanoreceptors and polymodal receptors exist in the laryngeal mucosa; they are particularly numerous in the laryngeal surface of the epiglottis and arytenoid region, and uncommon in the vocal fold. Mechanoreceptors on the laryngeal mucosa were classified into a rapidly adapting group and a slowly adapting group, while all polymodal receptors adapted rapidly to mechanical stimulation. These results suggest that these non-specific polymodal and rapidly adapting receptors may correspond to more superficial receptors such as free nerve endings and some taste buds, and also monomodal slowly adapting mechanoreceptors may correspond to deeper terminals in the subepithelium. It is also considered possible that the structures and the characteristics of these receptors are appropriate to elicit the protective laryngeal reflexes by non-specifically detecting various kinds of stimuli.

Animals↗

PubMed1997

[A case of an elderly patient with dementia and gait disturbance associated with influenza].

We report a case of progressive dementia and prolonged gait disturbance correlated with influenza A/H3N2 infection in 91-year-old female patient, admitted because of in ability to take care of herself due to aging and cerebral infarction. At admission, conversation and comprehension were not significantly impaired, and she was able to walk by herself. Flu symptoms such as high grade fever, chills, arthralgia, and cough appeared after a short stay at home. Influenza A/ H3N2 was confirmed serologically. Delirium occurred on the sixth day after influenza onset, persisted for three weeks, followed by recovery. Dementia symptoms such as memory defects and disorientation continued and did not improve. Due to this febrile episode, she was unable to walk unassisted. The results of computed tomography performed before and after the influenza episode were unremarkable for additional cellebro-vascular events during the observed period. Influenza infection may be an important risk factor for reducing the quality of life in the elderly. In geriatric cases, influenza should not be treated as a mere transient illness, but rather one which has important consequences for the elderly population, including the possibility of life threatening complications.

Aged↗

PubMed1996

Fictive vocalization in the cat.

A new animal model is described for the study of fictive vocalization, evoked by electrical stimulation of the periaqueductal grey (PAG) in decerebrate, paralyzed and artificially ventilated cats. Changes in activities of the phrenic, abdominal, recurrent and superior laryngeal nerves induced by PAG stimulation after induction of paralysis were compared with the activities of these nerves or the muscles innervated by them during actual vocalization induced before paralysis. The PAG-induced respiratory and laryngeal motor pattern in paralyzed cats is similar to that of PAG-induced vocalization. Furthermore, the switch from inspiration to vocal-like activity is usually synchronized with lung inflation in both paradigms. It is concluded that fictive vocalization can be induced by PAG stimulation in paralyzed cats.

Animals↗

PubMed1995

Convergence of afferents from the SLN and GPN in cat medullary swallowing neurons.

We demonstrated the convergence of information from the pharyngeal and laryngeal mucosa, transmitted by the glossopharyngeal nerve (GPN) and superior laryngeal nerve (SLN), in the nucleus of the tractus solitarius (NTS). First, the distribution of terminals of the GPN and SLN in the NTS was examined by an HPR tracing technique in cats, and the synapse formation of these neurons with NTS neurons was demonstrated by electron microscopy. The HRP-labeled SLN and GPN terminals were localized in a small area of the interstitial subnucleus of the NTS, slightly rostral to the obex, forming synapses with NTS neurons. Next, using extracellular recording in anesthetized cats, we determined whether or not swallowing-related neurons in the medulla oblongata receive peripheral inputs. Convergence of peripheral sensory inputs from the SLN and GPN was observed in more than 80% of the NTS cells. These results suggest that the NTS is not only a sensory-relay nucleus but also integrates information necessary for eliciting protective reflexes of the upper airway, such as swallowing.

Afferent Pathways↗

PubMed1995

Convergence of laryngeal afferents with different natures upon cat NTS neurons.

To clarify the convergence of laryngeal afferents within the nucleus tractus solitarius (NTS) in the cat, we examined in the medulla the response characteristics of superior laryngeal nerve (SLN) fibers and NTS neurons to mechanical and chemical stimulation applied to laryngeal mucosa by extracellular recordings. The response was recorded in 75 SLN primary afferent fibers (PAFs) and 92 NTS neurons. PAFs of the SLN consisted of numerous monomodal mechanosensitive fibers and a small number of chemosensitive and polymodal fibers. On the other hand, the majority of NTS neurons had a polymodal nature. Thus, laryngeal information is considered to be integrated in modality into NTS neurons. All mechanosensitive fibers received information from a small restricted field in the larynx. On the contrary, each NTS neuron responded to mechanical stimulation over a wide laryngeal field, indicating that information from different sites spatially converge on NTS neurons. Our results suggest that caudal NTS neurons play a cardinal role in integrating laryngeal afferents, which are thought to elicit laryngeal reflexes.

Afferent Pathways↗