Biomedical subjects

J C Hwang

Publications and source records attributed to J C Hwang.

At least 19 recordsLinked to original sources

PubMed1995

Bilateral amputations following hydrotherapy tank burns in a paraplegic patient.

Hydrotherapy is an important part of wound care and physical therapy. The benefits of hydrotherapy are derived from water's cleansing ability, buoyancy, drag, inertia and temperature. If the temperature of the water is not adequately controlled, an immersion scald burn can occur. A paraplegic patient who was receiving hydrotherapy for treatment of his malleolar ulcers sustained immersion scald burns that ultimately necessitated below-the-knee amputations.

Adult↗

PubMed1995

Changes in phrenic, hypoglossal and recurrent laryngeal nerve activities after intravenous infusions of aminophylline in cats.

Aminophylline is known to have respiratory stimulant properties, and it has been suggested that it may also be effective in sleep apnoea. However, its role in this disorder remains uncertain. Theoretically, increasing upper airway motoneural activity in order to maintain airway patency might alleviate obstructive sleep apnoea. On the other hand, increasing the respiratory drive may also prove beneficial in treating central sleep apnoea. In these studies, we attempted to determine the effect of aminophylline on neural activities of the upper airway and diaphragm. We administered intravenously either a low dose (4 mg.kg-1) or a high dose (16 mg.kg-1) of aminophylline to decerebrated, vagotomized and paralysed cats, and continuously recorded the phrenic hypoglossal and recurrent laryngeal nerve activities for 3 h. Results showed that a high dose of aminophylline induced a marked increase in phrenic nerve activity, but not hypoglossal or recurrent laryngeal nerve activity. In a group treated with a low dosage of aminophylline, a significant increase of activity was found in all three nerves. Furthermore, phrenic nerve activity increased more with a high dose than with a low dose. We confirmed that aminophylline has dose-dependent and selective effects on respiratory neural activity. A low dose acts on the upper airway and diaphragm, but a high dose induces a marked increase in central respiratory drive. According to our results, low dose aminophylline might be beneficial in obstructive sleep apnoea, whereas, a high or low dose might improve some cases of central sleep apnoea.

Aminophylline↗

PubMed1994

Plasma luteinizing hormone and progesterone concentrations after prostaglandin F2 alpha in Taiwan yellow cows (Bos indicus).

A luteolytic dose (500 micrograms) of cloprostenol was given four days before expected estrus to five mature cyclic cows of native Taiwan Yellow cattle. Blood samples were collected at hourly intervals for 60 hours and then twice daily (0800 h and 1600 h) until onset of the following estrus or Day 29 after prostaglandin (PG) injection. Plasma progesterone levels were quite low in the follicular phase and elevated over an 11-13 day period during the luteal phase for every animal. Two cows showed peak luteinizing hormone (LH) levels of 19.97 and 23.77 ng/ml of plasma at 120 and 127 h after PG injection. One cow did not show peak LH level during the 60-h sampling period, but had its highest concentration of 18.02 ng/ml at 0800 h on Day 8. Two cows showed no detectable peak LH during the 60-h sampling period or on subsequent days. But these two cows had increased concentrations of progesterone beginning on Day 6 and Day 12. All animals came back into estrus 23-28 days after PG treatment.

Animals↗

PubMed1994

Responses of respiratory-modulated facial nerve activity to activation of the ventrolateral subarea of the nucleus of the tractus solitarius.

The purpose of the present study was to examine respiratory-modulated facial nerve activity (FNA) in response to activation of the ventrolateral subarea of the nucleus of the tractus solitarius (vlNTS). The cat was anesthetized with sodium pentobarbital and then vagotomized bilaterally, paralyzed and ventilated artificially. End-tidal fractional concentration of CO2 was maintained at hyperoxic normocapnia. Partial occipital craniotomy was performed to expose the obex. Activities of the phrenic and the facial nerves were simultaneously recorded. The vlNTS was excited by electrical current (80 Hz frequency, 0.5 ms pulse duration and a variety of current from 12.5 to 50 microA) and glutamate (30-100 nl, 0.5 M). Three responsive patterns for both nerves were observed in response to vlNTS activation. First, inspiratory facial nerve activity (iFNA) and phrenic nerve activity (PNA) were decreased (p < 0.01), while expiratory facial nerve activity (eFNA) was not changed. Second, iFNA and PNA were diminished (p < 0.01) but eFNA was enhanced. Third, iFNA was decreased whereas PNA was enhanced. These results suggest that there might be a neural pathway projecting from the vlNTS to the facial nuclei to modulate respiratory-modulated facial nerve activities.

Animals↗

PubMed1992

Presence of neuronal cell bodies in the sympathetic pressor areas of dorsal and ventrolateral medulla inhibiting phrenic nerve discharge in cats.

To examine whether neuronal cell bodies (perikarya) in the pressor areas of dorsal medulla or ventrolateral medulla also modulate respiratory function, phrenic nerve activity was monitored and correlated with the pressor response in chloralose-urethane anaesthetized cats. The animals were paralyzed and artificially ventilated maintaining the end-tidal fractional concentration of CO2 at 0.04-0.05. The same pressor point in the dorsal or ventrolateral medulla was stimulated electrically (rectangular pulse of 20-200 microA, 80 Hz and 0.5 ms) and then chemically (0.25-0.5 M sodium glutamate, 80-200 nl). Areas producing pressor effects in either the dorsal or ventrolateral medulla produced a current-dependent decrease of phrenic discharge. The decrease in Pna was significant when the electrical current reached 50 microA or above. It occurred immediately before the onset of increase in blood pressure. Injection of glutamate to the same pressor point in either the dorsal or ventrolateral medulla produced a similar decrease in phrenic nerve activity. The results suggest that in the pressor areas of dorsal and ventrolateral medulla there are neuronal perikarya that can increase systemic arterial pressure and inhibit phrenic nerve activity. Whether the same or separate neurones are responsible for these responses is to be determined.

Animals↗

PubMed1992

Activity of abdominal muscle motoneurons during hypercapnia.

Our purpose was to examine the influence of hypercapnia on the activity of motoneurons innervating the transversus abdominis and internal oblique abdominal muscles, and of integrated phrenic and abdominal motor nerve activities. Studies were done in nine adult cats that were decerebrated, vagotomized, thoracotomized, paralyzed and ventilated mechanically. Of 42 motoneurons examined, 24 showed strong respiratory modulation (RM neurons), with the discharge confined primarily to the central expiratory period. The remaining 18 motoneurons discharged tonically, and failed to show respiratory modulation even at increased levels of central respiratory drive. Hyperoxic hypercapnia augmented the activities of the phrenic and abdominal nerves and increased the early expiratory discharge frequency of the RM neurons. The hypercapnia-induced increase in firing frequency during early expiration was accompanied by a corresponding decline in late expiration, and a virtual abolition of the inspiratory activity in the few neurons that discharged in this phase under normocapnic conditions. Finally, hypercapnia induced an increase in the number of spikes generated during each expiratory period in about half of the RM neurons, whereas the remaining cells showed a decrease. Thus, the increased peak activity of the integrated whole abdominal nerve burst with hypercapnia was brought about by a shift in the temporal pattern of motoneuron firing, or by an increase in the number of spikes generated during the expiratory period. The steep rate of rise and the pronounced early expiratory peak observed in the integrated abdominal nerve burst during hypercapnia in this preparation are consistent with the increase in motoneuron firing frequency during the early stages of the expiratory phase.

Abdominal Muscles↗

PubMed1992

Differential effects on sympathetic nerve activities elicited by activation of neurons in the pressor areas of dorsal and rostral ventrolateral medulla in cats.

Changes of the nerve activity of the sympathetic renal and vertebral nerves were elicited by microinjection of sodium glutamate (50 nmol/100 nl) into the pressor areas of the dorsal (DM) and rostral ventrolateral medulla (RVLM) in cats under urethane-chloralose anesthesia. Animals were bilaterally vagotomized, artificially ventilated, and paralyzed with gallamine triethiodide. The vertebral nerve activity always increased when pressor responses were induced by DM or RVLM stimulation. However, the effects of medullary stimulation on the renal nerve activity were variable. Three types of renal nerve responses concomitant with the pressor responses were observed in either baroreceptor-intact or baroreceptor-denervated cats. They were: (1) augmentation (type I); (2) attenuation (type II); and (3) insignificant change (type III). Type I responses were often elicited by RVLM stimulation whereas type II responses were often elicited by DM stimulation. Findings suggested that neurons integrating these sympathetic nerve activities were not equally distributed in the pressor areas of DM and RVLM. This result supports the notion that neurons located in different pressor areas of the brainstem exert differential effects over different sympathetic nerve activities.

Animals↗

PubMed1992

Correlation of cardiovascular and respiratory responses to glutamate excitation of pressor areas of the medulla in cats.

Cardiorespiratory responses, including changes of systemic arterial pressure (SAP), renal or splanchnic sympathetic nerve activity (SNA) and phrenic nerve activity (PNA), were elicited by microinjection of monosodium glutamate solution (0.5 M, 100 nl) into the dorsal (DM) and rostral ventrolateral medulla (RVLM) in 15 vagotomized cats anesthetized by urethane-chloralose and paralyzed by gallamine triethiodide. Artificial ventilation was adjusted to keep the end-tidal CO2 concentration at 4.0-0.5%. Sixty two pressor and 17 non-pressor sites were stimulated. Most of the stimulations inhibited the PNA. The responses of SNA was variable, showing increases, decreases or no change. Inhibition of SNA during SAP increase was not secondary to baroreceptor activation as the inhibition persisted in carotid sinus/aortic denervated animals. Although various combinations of changes of SNA and PNA were observed, their temporal courses were similar in many instances. Attenuation of SNA and PNA was synchronized, suggesting that these changes are coupled in the stimulating sites. The findings suggest that some neurons in DM and RVLM act as a functional unit to modulate cardiorespiratory functions whereas others simply coexist in the same area independent from each other.

Animals↗

PubMed1991

Basic determinants for FM responses in the inferior colliculus of rats.

The response of 835 click-sensitive neurons in the inferior colliculus (IC) to ramp frequency modulated (FM) tones was studied in the anaesthetized rat. More than 70% of the cells were sensitive to the FM sound, and over 25% were "FM specialized". Systematic variations of the stimulus parameters showed that sweep velocity, sweep range, and intensity of the FM signal were the 3 basic determinants for the unit response. For an "FM specialized" cell, the response pattern to each of the parameters was either monotonic or bell-shaped. The population statistics of response patterns to the FM parameters, including the tuning factors, were generated. A stimulus domain was proposed to represent the "receptive space" of the FM cells.

Acoustic Stimulation↗

PubMed1991

Differential actions of the medial region of caudal medulla on autonomic nerve activities.

1. The inhibitory effects produced by activation of the medial region of caudal medulla on activities of the left and right cardiac sympathetic, vagus and greater splanchnic nerves were studied in chloralose-urethane anaesthetized cats. 2. Electrical stimulation of the medial region produced an 80-92% inhibition of the sympathetic nerve activities, and a 45% and 58% inhibition of the left and right cardiac vagal nerve activities, respectively. There were no significant differences between effects elicited in the left and right autonomic nerves. Similar but smaller inhibitory effects were produced by micro-injection of sodium glutamate (0.5 mol/L) or DL-homocysteic acid (50 mmol/L) to the same medullary sites. 3. These data suggest that neurons residing in the medial medullary region exert strong inhibitory effects on autonomic nerve activities. Since the vasculature is principally innervated by sympathetic nerves, inhibition of sympathetic nerve activities might be the principal factor responsible for the depressor effects caused by activation of the medial region of caudal medulla. The heart is innervated both by sympathetic and parasympathetic nerves. Thus, their simultaneous inhibition during activation of the medial region elicits only a weak and variable inhibition of the heart.

Anesthesia↗

PubMed1990

Altered sensitivities of auditory neurons in the rat midbrain following early postnatal exposure to patterned sounds.

Pure tone sensitivity of inferior colliculus (IC) neurons in adult rats was studied electrophysiologically following exposure to a frequency-modulated (FM) tone during the first 5 postnatal weeks. The distribution of best frequencies (BF) and minimum thresholds (MT) of 274 single units, when compared to the control, showed an abnormal clustering centered around the region of the audiogram occupied by the FM tone to which the rats had been exposed. This effect was interpreted as the result of activity-dependent changes of IC during development.

Acoustic Stimulation↗

PubMed1990

Some biomechanical considerations of polytetrafluoroethylene sutures.

The biomechanical performance of polytetrafluoroethylene (PTFE) sutures has been compared with that of polypropylene sutures, the standard to which other sutures used in vascular and cardiac surgery are compared. The PTFE is supple and has no plastic memory, while the polypropylene suture is stiff and retains its plastic memory. In addition, the rate of creep encountered in the PTFE suture was significantly less than that of the polypropylene suture. The knotting profiles for knot security for either a square, granny, or surgeon's knot for polypropylene sutures were three throws each. In contrast, knot security with either a square or granny PTFE knot was accomplished with seven throws; six throws were needed for a secure surgeon's knot. The breaking strength of the unknotted and knotted PTFE sutures was approximately one half as great as that for the unknotted and knotted polypropylene sutures. Knot construction significantly reduced the breaking strength of polypropylene sutures but did not alter the breaking strength of PTFE sutures. The percent elongation experienced by both sutures before breakage did not differ significantly. The elasticity, as measured by work recovery, for the polypropylene suture was greater than that for the PTFE suture. On the basis of its unique biomechanical performance characteristics, the PTFE suture should have an important place in vascular and cardiac surgery.

Physical Phenomena↗

PubMed1990

Changes in power spectrum of electromyograms of masseter and anterior temporal muscles during functional appliance therapy in children.

This study applied frequency analysis to compare changes in the power spectrum density functions of surface electromyograms obtained from the paired masseter and anterior temporal muscles during therapy with three types of functional appliances, namely the Bionator, modified Fränkel type I, and Fränkel type III. Eighteen children were divided into three groups receiving either Bionator, Fränkel type I, or Fränkel type III therapy; a fourth group consisting of six children who received no therapy served as control. Before and after 3, 6, and 12 months of therapy, each child performed maximum voluntary isometric clenches in the position of maximum intercuspation. The mean frequency of the power spectrum was the variable studied. Children treated with the Bionator and Fränkel type I appliances showed greater changes in mean frequency than those treated with the Fränkel type III appliance. Although the muscles of untreated children also showed shifts of mean frequency to lower frequency values as a function of time, there was a greater downward shift of mean frequency in those treated with functional appliances. The downward shifts might have been associated with changes in muscle fiber lengths and/or recruitment patterns as a result of both treatment and normal growth.

Activator Appliances↗

PubMed1990

The different changes of phrenic nerve activity and frequency elicited by microinjection of L-glutamic acid into ventrolateral nucleus of the tractus solitarius in cats.

There is only limited information of the neurotransmitters in central respiratory control. L-glutamic acid has been proposed as the primary neurotransmitter in the nucleus of the tractus solitarius (NTS) in cats. To test whether there is a respiratory effect of glutamic acid in the respiratory center or not, we microinjected L-glutamic acid (1 M, 0.1 microliter) via 1 microliter Hamilton microsyringe into the ventrolateral nucleus of NTS, namely dorsal respiratory group (DRG) over two-second intervals with continuous monitoring of phrenic nerve activity (PNA), frequency (f), end tidal CO2, blood pressure and heart rate. Glutamate induced various respiratory changes including: increase in PNA and f decrease in PNA and f [corrected] increase in PNA but decrease in f and decrease in PNA but increase in f. In addition to regular changes of PNA or f elicited by glutamate microinjection were found. Other patterns of irregular rhythmic changes such as absence of PNA, continuous phrenic nerve discharge and irregular phrenic nerve discharge with reflex apnea, apneusis and irregular respiration respectively were also observed. Glutamic acid appears to significantly modulate respiratory drive in DRG. We suggested that L-glutamic acid may be a neurotransmitter in the respiratory center and be involved in central respiratory control.

Animals↗

PubMed1989

Light diffraction intensity from muscle fibres in different osmotic solutions: measurement of equilibration time.

A new method for evaluating the osmotic equilibration time of striated muscle fibres is described. Single fibres from the semitendinosus muscles of frog were illuminated normally with a He-Ne laser. The first-order diffraction intensity was measured continuously after the tonicity of the fibre's bathing solution was changed abruptly. Hypertonicity decreased while hypotonicity increased the intensity. The time course of the intensity decrease or increase followed closely a simple exponential with a single time constant. It is proposed that the time constant associated with the diffraction intensity transient is a true representation of the equilibration process. A simple diffraction model provides a relationship between diffraction intensity and the diameter of the muscle fibre. This relationship is used to explain the diffraction intensity of fibres in different osmotic solutions.

Animals↗

PubMed1989

Real-time signal acquisition and analysis for clinical dental electromyography using a microcomputer-based system.

The Electromyographic (EMG) Signal Acquisition and Analysis System is an integrated hardware and software system that digitizes multichannels of amplified EMG signals and stores them in user defined disc files before analysis. The software runs on all IBM PC and its compatibles with the appropriate analogue-to-digital (A/D) conversion board. Both time and frequency domain analyses can be computed on-line. This system provides a low cost method of digitizing and analysing EMG signals on real-time for clinical dental electromyography.

Adult↗

PubMed1989

Characterization of expiratory intercostal activity to triangularis sterni in cats.

Our purpose was to characterize activity of the intercostal nerve branch innervating the triangularis sterni muscle and the motoneuronal activities comprising this nerve discharge. In decerebrate, vagotomized, paralyzed, and ventilated cats, phasic triangularis sterni neural activity was evident in normocapnia. In most cats, activity did not commence until midexpiration. Activity then rose progressively to terminate at end expiration. Peak neural activities increased in parallel with phrenic activity in hypercapnia and fell in hypocapnia. The progressive increase in triangularis sterni neural activity within each respiratory cycle resulted from recruitment of motoneuronal activities throughout expiration. Once recruited, many motoneurons had a decrementing or constant discharge frequency. In hypercapnia, motoneuronal discharge frequencies increased, and additional activities were recruited. The number of active motoneurons and their discharge frequencies fell in hypocapnia. A similar pattern of motoneuronal activities and responses to stimuli was observed in cats with intact vagi. Factors are considered that may underlie the recruitment pattern of triangularis sterni motoneuronal activities and the inhibition of these in early expiration.

Animals↗

PubMed1989

EMG power spectrum patterns of anterior temporal and masseter muscles in children and adults.

The power spectrum of electromyograms (EMG) has been demonstrated to vary with muscles having different muscle fiber type compositions. This study investigated the variations in EMG power spectrum patterns of the masticatory muscles with age and gender by comparison of the mean power frequency (MPF) of the anterior temporal and masseter muscles in children and adults. Surface EMG signals were sampled bilaterally from the muscles when the subjects were performing maximum voluntary isometric clenches at maximal intercuspal position. The results indicated that MPF values were age-dependent (p less than 0.001), and sexual dimorphism was evident (p less than 0.001), with lower MPF values in male and adult muscles. While male adults had the lowest and female children had the highest MPF values, female adults had MPF values closer to values obtained from male children. These differences or similarities could be attributed to the degree of differentiation of the muscles during growth and development of the craniofacial morphology.

Adult↗