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Biomedical subjects

K Oi

Publications and source records attributed to K Oi.

27 records · Page 2Linked to original sources
PubMed1994

Variation of the jaw-opening reflex during spontaneous mastication in rabbits.

To understand the modulation of periodontal mechanoreceptor activity on mastication, the jaw-opening reflex (JOR) evoked by electrical stimulation of the inferior alveolar nerve (IAN) was studied during chewing in freely behaving rabbits. Spontaneous chewing movements were intact from the IAN stimulation below two times the threshold (T) which was measured at rest. As the stimulus intensity was increased to more than 2.5 T, the amplitude of the masseter activity decreased or it was abolished; however, the chewing rhythm was still maintained up to 3.0 T. When the low-threshold primary afferents were tested while the rabbit chewed pellets rhythmically, the amplitude in the JOR was inhibited below the prior control level. The inhibitory effect on the JOR was larger in the opening phase than that in the closing phase. In conclusion, the JOR was tonically depressed during the masticatory cycle and the inhibition of the JOR was rhythmically modulated in a phase-linked manner that was larger in the opening phase than in the closing phase.

Animals↗
PubMed1991

Use of N2O/O2/enflurane anesthesia for dental treatment of the handicapped.

To develop an anesthesia maintenance method that could be expected to maintain a reasonably stable state during dental treatment of the handicapped, three methods (N2O/O2 [0% enflurane (E), n = 12], N2O/O2/0.6% E [n = 8], N2O/O2/1.5% E [n = 7]) were evaluated in terms of changes in plasma levels of cortisol, epinephrine (EP), and norepinephrine (NE). During a treatment period of 60 minutes, cortisol levels increased in the 0% E group (from 9.5 +/- 1.8 micrograms/dL to 19.4 +/- 2.4 micrograms/dL, P less than .01), did not change in 0.6% E group, and decreased in 1.5% E group (from 9.3 +/- 1.7 micrograms/dL to 5.8 +/- 1.0 micrograms/dL, P less than .01). Epinephrine and NE levels increased in the 0% E group, but were suppressed in the 0.6% E and 1.5% E groups. It is suggested that N2O/O2 inhalation anesthesia supplemented with low-dose enflurane produces a stable state during dental treatment with respect to cortisol, EP, and NE responses.

Adolescent↗
PubMed1990

Human jaw-opening muscle responses elicited by multiple-site electrical stimulation.

Electrical stimuli were applied to subjects' upper and/or lower gingivae around the right canines; (i) during maintained relaxation of masticatory muscles; (ii) at an active opening position; (iii) while clenching in an incisal edge-to-edge contact (IEC) position; and (iv) at the wide-open position. Reflex responses of the suprahyoid and jaw-closing muscles were obtained using surface electrodes. The electrical stimulation produced segmented reflex excitation(s) in the suprahyoid muscle and conventional reflex excitation and/or inhibition in the jaw-closing muscles when some background activity was maintained in the muscle(s). The excitatory reflex in the suprahyoid muscle responded to multiple site electrical stimulation which was delivered on both the upper and lower jaw simultaneously rather than to single site stimulation. Also, the responses depended on the intensity of the electrical stimulation. In particular, stronger intensities resulted in longer latencies. The results support the suggestions in our previous studies with mechanical stimuli, i.e. that the human jaw-opening reflex can be obtained only when some background activity is maintained in the jaw openers, perhaps due to low threshold afferent input, and that spatial summation may be effective for the reflex.

Adult↗
PubMed1989

Dyspnea resulting from accumulation of pleural effusion after radical neck dissection. A case report.

The patient became dyspneic 3 days after radical neck dissection on the left side. A chest radiography showed bilateral pleural effusion.During the operation, a lymphatic leak was noted. In this case, the factor of an associated perforation of the pleural had not been demonstrated. Fresh frozen plasma was administered and positive end-expiratory pressure was applied. The patient had no residual pulmonary sequelae.

Blood Transfusion↗
PubMed1988

Two-dimensional jaw tracking and EMG recording system implanted in the freely moving rabbit.

A system for simultaneously recording mandibular position in the sagittal plane together with masticatory muscle activity was designed and tested in rabbits. Two small magnetic sensors were implanted in the maxillary bone and a powerful magnet made of a rare earth metal attached to the mandibular central incisors. The magnetic sensors detected the mandibular movements in the sagittal plane by movement of the magnet. Masseter EMG was recorded by fine wire electrodes and amplified by a specially designed amplifier. The necessary preamplifiers were assembled as an integrated circuit (IC) chip in a small housing. The signals from the preamplifier were then passed through a signal processing unit and taped on an instrumentation tape. The system was applied to the freely moving rabbit supplied with food and water during the night. It worked without any trouble for more than 24 h. Since the implanted magnetic sensors were stable for more than 4 months, long-term recording could be done by merely reimplanting the magnet, the cables and the EMG electrodes, which was simple.

Animals↗
PubMedDate not supplied

Noxious stimulation reduces blood pressure but not flow in the internal carotid artery as measured in rabbits.

The purpose of this study was to examine effects on blood flow by alteration of blood pressure resulting from noxious stimuli. The experiment was carried out in anesthetized and paralyzed rabbits. Blood pressure was measured through a teflon catheter inserted in the common carotid artery (CCA). Blood flow at the CCA, internal carotid artery (ICA), or external carotid artery (ECA) was measured using an electromagnetic flowmeter placed at the CCA. The effects of pinching and electrical stimuli upon the blood pressure and flow were tested. Blood pressure at all three arteries decreased transiently from these noxious stimulations. There were no statistical changes in the blood flows respectively. However, different mechanism could exist between ECA and ICA because blood flow of ECA was decreased and that of ICA was increased or had no change. We concluded that vascular resistance reduction in the ICA against the arterial pressure decrement produced by noxious stimuli may be a control mechanism to keep cerebral blood flow constant. In contrast, there may be no such mechanism in the ECA circulation.

Anesthesia, Dental↗