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Biomedical subjects

Y C Tong

Publications and source records attributed to Y C Tong.

At least 19 recordsLinked to original sources
PubMed1992

Effects of acute in vitro overdistension of the rabbit urinary bladder on DNA synthesis.

Urinary bladder outflow obstruction induces a myriad of structural and functional changes in the organ. Among the morphological responses to outlet obstruction is both hyperplasia and hypertrophy of specific cellular elements. The initial event which has been implicated in the initiation of the response to outflow obstruction is an initial period of high intravesical pressure and subsequent distention of the bladder. In a previous study, it was shown that at one day following partial outlet obstruction there was a marked increase in thymidine labelling of the urothelium, at 3-5 days, the labeling shifted from the urothelium to the interstitial and serosal elements. The current study was designed to determine if acute distention of the urinary bladder can induce an increase in DNA synthesis (3H-thymidine incorporation), and localize the increased DNA synthesis via autoradiography of 3H-thymidine. In this study, the bladders of adult male New Zealand white rabbits were mounted in isolated in vitro baths. Each control bladder was filled to either 5 or 20 ml. with saline, or distended to 120% of capacity. The bladders were incubated for 7 hours at which time 3H-thymidine was placed both within and outside the bladder for an additional one hour. At the end of the time the bladder was divided at the ureteral orifices into bladder body and base, and each body and base divided into two sections. One section of bladder body and base was quantitatively analyzed for both labelled and unlabelled DNA; the second section was fixed and prepared for autoradiography. The results can be summarized as follows: 1) Acute overdistention for 8 hours induced a slight decrease in the DNA concentration which was mediated by edema of the bladder wall. 2) Acute overdistention induced a 5-fold increase in 3H-thymidine incorporation in the bladder body and a 3-fold increase in the bladder base. Radioautoradiography of the overdistended bladders showed significant and substantial labelling which was confined to the urothelial basal cells. The control bladders showed little or no labelling. These results are consistent with the theory that acute distention following partial outlet obstruction initiates the proliferative response of the bladder to outlet obstruction, and the urothelium is the initial target of the proliferative response. Functionally, the proliferative response may serve to maintain the structural as well as functional integrity of the bladder.

Animals↗
PubMed1992

Use of hematoma size on computerized tomography and calculated average bleeding rate as indications for immediate surgical intervention in blunt renal trauma.

One of the most demanding situations for a urologist is to decide which blunt renal trauma patients need immediate surgical exploration. Although computerized tomography can offer a lot of invaluable information, clear guidelines for selection of surgical versus conservative treatment are still lacking. A retrospective study of 15 blunt renal trauma cases showed that the hematoma size measured from computerized tomography using the method of summation planimetry bears a much closer correlation with the clinical outcome of the patient than does the degree of kidney parenchymal defect. Moreover, the average bleeding rate, calculated by dividing the size of the hematoma by the time elapsed from injury to scanning, gives a more accurate prediction for the need for immediate surgical treatment.

Adolescent↗
PubMed1992

Influence of the bathing medium on the contractile responses of the rabbit urinary bladder.

This study examined contractile responses of the in vitro rabbit whole-bladder preparation to field stimulation, bethanechol and KCl in Tyrode's solution and minimum essential medium (MEM). We found frequency-dependent increases in intravesical pressure in bladders incubated in Tyrode's solution and MEM. However, bladders incubated in MEM consistently responded with greater increases in intravesical pressure compared to those incubated in Tyrode's solution. Similarly, there were frequency-dependent increases in the rate of pressure generation in bladders incubated in Tyrode's solution and MEM, and bladders incubated in MEM responded with greater rates of pressure generation than those incubated in Tyrode's solution at frequencies of 1, 2 and 4 Hz. In addition, there were significant increases in intravesical pressure generated in response to administration of 500 mmol/l bethanechol and 186.4 mmol/l KCl in bladders incubated in MEM compared to Tyrode's solution but no changes in the rate of pressure generation. The influence of L-methionine, one of the constituents of MEM, on the responses of whole bladders to nerve stimulation was also investigated. L-methionine at concentrations of 0.1 and 1.0 mmol/l had no effects on the increase in intravesical pressure or rate of pressure generation following nerve stimulation. It is speculated that the increases in contractile responsiveness of bladders incubated in MEM are related to the combination of amino acids, vitamins and other constituents of the cell culture medium.

Animals↗
PubMed1992

Correlations of purinergic, cholinergic and adrenergic functions in rabbit corporal cavernosal tissue.

Erection involves cholinergic, adrenergic as well as non-cholinergic non-adrenergic nerves. Endothelial-derived relaxation factor plays an important role in mediating smooth muscle relaxation, which is crucial in initiating and maintaining erection. We previously showed that adenosine 5'-triphosphate (ATP) can induce significant relaxation in rabbit corporal cavernosal tissue. The present study presents effects of different neurotransmitters and the role of endothelium in controlling the contractile/relaxant status of rabbit cavernosal tissue. These studies utilized isolated tissue strips prepared from the corpus cavernosum of sexually mature male New Zealand white rabbits. The results can be summarized as follows: (1) field stimulation caused relaxations with rebound contractions in most strips; (2) bethanechol (250 microM), isoproterenol (20 microM) and ATP (1 mM) all induced relaxations, though the relaxation induced by bethanechol was poorly sustained; (3) removal of the endothelium by rubbing decreased the relaxation to field stimulation and virtually eliminated the relaxation induced by bethanechol, but had no effect on the relaxation responses to isoproterenol and ATP; (4) methoxamine (200 microM) stimulated a sustained contraction of corporal cavernosal tissue, an effect unaltered by rubbing the strips; (5) low dose epinephrine induced relaxation, whereas higher concentrations contracted the tissue, and (6) beta-adrenergic inhibition with propranolol (20 microM) was significantly more effective than mascarinic blockade with atropine (20 microM) in eliminating relaxation caused by field stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Psychophysical studies using a multiple-electrode cochlear implant in patients who were deafened early in life.

Psychophysical studies were conducted on 10 cochlear implant patients, between 5 and 23 years of age at the time of surgery, who were deafened prior to 4 years of age. The multiple-electrode prosthesis manufactured by Cochlear Ltd. was used. Identification studies, the recognition of 2-4 stimuli after some training, were conducted on 3 of the 10 patients. For current level and repetition rate identification, performance was comparable to that observed for postlingual adult patients. For electrode position identification, however, performance was much poorer than that observed for postlingual adults. In general, the difference limens for current level, repetition rate and duration, and the gap detection thresholds were similar to those observed for postlingual adults. For 3 patients whose etiology was Usher's syndrome, the repetition rate limens at higher rates were larger than those of the other patients. The limens for electrode position, measured in a discrimination task, were 1-3 electrodes for most patients. However, for 3 patients, limens of 6-10 electrodes were recorded. For numerosity judgements, the counting of stimuli in a temporal series as a function of the rate of presentation, the patients were less successful at counting for rates of 3-8/s than for lower rates (1-2/s).

Adolescent↗
PubMed1991

Results of speech perception and speech production training for three prelingually deaf patients using a multiple-electrode cochlear implant.

Five studies were conducted to measure changes in the perception and production of selected speech targets, with training, in three prelingually deaf patients. The two adults and one adolescent were implanted with the Cochlear (Nucleus) multiple-electrode prosthesis. The studies were perception and production of nasal consonants; perception of syllable-final consonants; perception and production of alveolar consonants; auditory-visual perception of alveolar consonants; and perception and production of vowels. Perceptual data were collected in the audition (implant)-alone condition, except for the auditory-visual perception of alveolar consonants where the audition-alone, vision-alone, and auditory-visual conditions were used. Speech perception data in the audition-alone condition were also collected from four postlingually deaf adult implant patients, without training, to indicate differences between the two classes of patients. The three prelingually deaf patients generally showed some improvements in speech production. In perception, improvements were recorded only for individual patients in some studies. The performance of the adolescent was better than that of the two adults in all cases. The perceptual performance of the postlingually deaf patients was superior to that of the prelingually deaf patients in all cases.

Adolescent↗
PubMed1990

Renal angiomyolipoma: report of 24 cases.

A series of 24 patients with renal angiomyolipoma was reviewed. Their ages ranged from 10 to 70 years (average 41). Four cases were associated with tuberous sclerosis, 1 with spinal neurilemmoma, 1 with transitional cell carcinoma and another with renal tuberculosis. The presenting symptoms in decreasing frequencies were flank pain, mass, haematuria, fever, syncope and respiratory distress. Although it has often been said that angiomyolipomas associated with tuberous sclerosis are small and asymptomatic, all 4 such patients in this study had large symptomatic tumours. Before the advent of CT scan and ultrasonography, the pre-operative diagnostic rate for cases unassociated with tuberous sclerosis was 10% (1/10). With the combined use of these 2 modalities, the diagnostic rate increased to 60% (6/10). Most patients in this series were treated with nephrectomy. However, equally good outcomes occurred in 2 patients who received partial nephrectomies. Pre-operative diagnosis now makes it possible to consider more conservative management.

Adult↗
PubMed1990

Dimensions of the scala tympani in the human and cat with reference to cochlear implants.

The width, height, and cross-sectional area of the scala tympani in both the human and cat were measured to provide dimensional information relevant to the design of scala tympani electrode arrays. Both the height and width of the human scala tympani decreased rapidly within the first 1.5 mm from the round window. Thereafter, they exhibit a gradual reduction in their dimension with increasing distance from the round window. The cross-sectional area of the human scala tympani reflects the changes observed in both the height and width. In contrast, the cat scala tympani exhibits a rapid decrease in its dimensions over the first 6 to 8 mm from the round window. However, beyond this point the cat scala tympani also exhibits a more gradual decrease in its dimensions. Finally, the width of the scala tympani, in both human and cat, is consistently greater than the height.

Anatomy, Comparative↗
PubMed1990

Perceptual-oral training of two hearing-impaired children in the recognition and production of /s/ and /z/.

Two hearing-impaired children were tested and trained in the utilization of an artificial acoustic cue that signalled the presence of /s/ and /z/ in verbal stimuli. These sounds, chosen because they are among the most important morphemes in English, were both perceived and produced significantly better by the subjects following only seven training sessions when the cue, automatically signalled by a specially designed laboratory device, was presented at a 20 dB sensation level in a frequency range immediately above the subjects' upper limits of hearing for amplified speech. The implications of the study are briefly discussed in relation to testing and training procedures involving sensory aids.

Auditory Threshold↗
PubMed1990

Comparison of two speech processing schemes using normal-hearing subjects.

Two speech processing schemes have been implemented on a real-time laboratory speech processor for speech perception studies on normal-hearing subjects. The first scheme presents the information of two spectral components, the first and second formant of the speech signal, and will be referred to as the ZC (zero-crossing) scheme. The second scheme presents the information of four spectral components, four spectral peaks of the speech signal determined from the output of a filter bank, and will be referred to as the FB (Filter-bank) scheme. Perceptual studies were conducted on 4 normal-hearing subjects. Two of the 4 subjects were first trained and tested using the ZC scheme while the other 2 used the FB scheme. The training and testing schedules were then repeated for the unused scheme. Vowel perception performance was similar across subjects and speech processing schemes. Percentage correct scores for consonant perception in noise were higher for the FB scheme than for the ZC scheme at signal-to-noise ratios ranging from 5 to 20 dB. Percentage correct scores for open set CNC words and speech tracking scores were also better for FB than for ZC.

Cochlear Implants↗
PubMed1989

Results for two children using a multiple-electrode intracochlear implant.

Assessments in speech perception, speech production, and language skills were conducted on two children, 5 and 10 years old at the time of surgery, using the Nucleus multiple-electrode cochlear implant. Data were collected pre- and post-operatively to measure changes in performance over time. For closed-set speech perception tests in the audition alone condition, post-operative performance was generally better than pre-operative performance and performance improved post-operatively for both patients. In closed-set vowel and consonant identification and open-set sentence perception for the older patient, post-operative improvements from the vision alone to the auditory-visual condition were recorded and performance improved post-operatively in both conditions. In all measures of speech production for both patients, post-operative scores were higher than pre-operative scores and performance improved post-operatively. In language skills, post-operative scores were higher than pre-operative scores and scores improved post-operatively in all measures for both patients.

Child↗
PubMed1989

Forward masking patterns produced by intracochlear electrical stimulation of one and two electrode pairs in the human cochlea.

Three psychophysical forward masking studies were conducted on a multichannel cochlear implant patient. The first study investigated the masking pattern produced by a bipolar electrode pair at different stimulus currents. It was found that the masking pattern for a single-masker bipolar electrode pair had a maximum located at an electrode position where the masker and probe coincided. The spread of the masking pattern was not symmetrical about the maximum. The amount of masking decreased very rapidly toward the apical direction and less rapidly toward the basal direction from the position of the maximum. As the stimulus current increased, the amount of masking at the maximum increased and the masking pattern broadened toward the base. The second study investigated the masking pattern produced by the activation of single bipolar electrode pairs with different spatial extents. The spatial extent of a bipolar electrode pair is defined as the distance between the apical and basal electrode members of the bipolar pair. With a small spatial extent (1.5 mm), the more basal electrode pairs (higher threshold and smaller dynamic range) produced broader masking patterns than the more apical electrode pairs (lower threshold and wider dynamic range), suggesting that there was more current spread at the basal region. With a larger spatial extent (4.5 mm), an additional secondary masking maximum was observed in the vicinity of the apical electrode member of the masker; this was observed only when the apical electrode member lay within the low-threshold apical region. The third study investigated the masking patterns produced by two loudness balanced bipolar masker electrode pairs activated within a stimulus period (inverse of the pulse repetition rate). The biphasic current pulses delivered to the two electrode pairs were nonoverlapping in time. It was found that, at any probe electrode position, the amount of masking produced by the two combined bipolar electrode pairs approximately followed the greater of the two maskings produced respectively by the two individual bipolar masker electrode pairs.

Cochlea↗
PubMed1988

Underlying structure of auditory-visual consonant perception by hearing-impaired children and the influences of syllabic compression.

The identification of consonants in (a)-C-(a) nonsense syllables, using a fourteen-alternative forced-choice procedure, was examined in 4 profoundly hearing-impaired children under five conditions: audition alone using hearing aids in free-field (A), vision alone (V), auditory-visual using hearing aids in free-field (AV1), auditory-visual with linear amplification (AV2), and auditory-visual with syllabic compression (AV3). In the AV2 and AV3 conditions, acoustic signals were binaurally presented by magnetic or acoustic coupling to the subjects' hearing aids. The syllabic compressor had a compression ratio of 10:1, and attack and release times were 1.2 ms and 60 ms. The confusion matrices were subjected to two analysis methods: hierarchical clustering and information transmission analysis using articulatory features. The same general conclusions were drawn on the basis of results obtained from either analysis method. The results indicated better performance in the V condition than in the A condition. In the three AV conditions, the subjects predominantly combined the acoustic parameter of voicing with the visual signal. No consistent differences were recorded across the three AV conditions. Syllabic compression did not, therefore, appear to have a significant influence on AV perception for these children. A high degree of subject variability was recorded for the A and three AV conditions, but not for the V condition.

Adolescent↗
PubMed1988

Synthetic vowel studies on cochlear implant patients.

Speech perception studies were conducted on three cochlear implant patients to investigate the relative merits of six speech processing schemes for presenting speech information to these patients. Electrical stimuli, described in this article as synthetic vowels, were constructed using tabulated data of formant frequencies of natural vowels. The six schemes differed in the number of formant frequencies encoded on the electrical signal dimension of electrode position, and/or in the range of electrode position used for encoding each formant frequency. Eleven synthetic vowels (i, I, E, ae, a, c, U, u, v, E, D) were used and were presented in a single-interval procedure for absolute identification. Single-formant vowels were used in two of the six schemes, two-formant vowels in three schemes, and three-formant vowels in the remaining scheme. The confusion matrices were subjected to conditional information transmission analysis on the basis of previous psychophysiological findings. Comparisons among the schemes in terms of the analyzed results showed that training, experience, and adaptability to new speech processing schemes were major factors influencing the identification of synthetic vowels. For vowels containing more than one formant, the information about each formant affected the perception of the other formants. In addition, there appeared to be differences between the perceptual processes for vowels containing more than one formant and the processes for single-formant vowels. Taking into consideration the effects of training, experience, and adaptability, the three-formant speech processing scheme appeared, on the basis of perceptual performance comparisons among the six schemes, to be the logical choice for implementation in speech processors for cochlear implant patients.

Aged↗
PubMed1988

Perceptual studies on cochlear implant patients with early onset of profound hearing impairment prior to normal development of auditory, speech, and language skills.

Psychophysical studies were conducted on three prelingual and two postlingual cochlear implant patients. Auditory sensations were produced by electrical stimulation of the residual nerve fibers of the auditory nerve by means of a multiple-electrode cochlear implant. The psychophysical performance of the prelinguals was, in general, poorer than that of the postlinguals; prelingual performance was poorer for repetition rate and electrode position identification, gap detection, and durational and numerosity judgments. Improved performance with time, however, was consistently observed for the prelinguals in the above-mentioned psychophysical tasks. There were significant individual differences in the amount of improvement among the three prelinguals. Speech perception studies were also conducted on the three prelingual patients. The speech perception performance of the three prelingual patients was much poorer than that of postlingual patients in general, and was consistent with their poorer psychophysical performance described above.

Adolescent↗
PubMed1988

Initial experience with children using the Nucleus 22 Channel cochlear implant.

The Nucleus 22 Channel cochlear prosthesis developed by the University of Melbourne and Cochlear Pty Ltd is now being used in over 90 clinics worldwide, in fourteen countries and fifteen languages. A total of thirty adolescents and thirty-nine children have now been implanted in Australia, America and more recently Germany. There have been no significant postoperative complications, and the device has been successfully programmed in children as young as two years nine months. Comprehensive evaluation and training programs are being undertaken with each implanted child to assess long term development of speech perception and communication skills. The average postoperative stimulation time for most of the children implanted is around 3 months, so as yet, little data has been recorded on these patients. However, the two original children implanted in Melbourne have now been using their speech processors in excess of 18 months. The focus of this paper will be on the performance of these two children.

Child↗