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Biomedical subjects

C T Hung

Publications and source records attributed to C T Hung.

At least 37 records · Page 2Linked to original sources

Effect of age on recovery from remifentanil anaesthesia.

In a prospective, randomized study, the effect of age on recovery from remifentanil anaesthesia was evaluated. Twenty consecutive patients classified as ASA 1 and 2 and having elective laparotomy were recruited to one of two groups based on age (Group 1 age <60 y and Group 2 age >60 y). Remifentanil boluses and infusion were used for induction and maintenance of anaesthesia. Dosage was titrated against clinical response to perioperative stimulation and the infusion was terminated at the end of the operation. Time intervals between termination of remifentanil infusion and 1) spontaneous respiration, 2) adequate respiration, 3) eye opening, 4) limb movement, 5) extubation, 6) Aldrete score >9, 7) discharge to recovery room and 8) discharge to the ward were recorded. Patient controlled analgesia with morphine was used for postoperative pain control. Student's t test was used to compare the differences in these time intervals between Groups 1 and 2. A P value <0.05 was taken as significant. We found that the younger age group regained spontaneous respiration (0.8+/-0.7 min vs 3.2+/-3.6 min), adequate respiration (3.4+/-3.7 min vs 7.6+/-5.8 min), opened their eyes (0.9+/-1.0 min vs 3.6+/-4.4 min), had their endotracheal tubes removed (5.0+/-4.6 min vs 9.0+/-6.5 min) and were discharged to recovery room (8.8+/-4.3 min vs 14.5+/-7.1 min) earlier than their older counterparts. In conclusion, age was a co-variate for recovery from remifentanil anaesthesia.

Adult↗

Anaesthetic clinical indicators in public hospitals providing anaesthetic care in Hong Kong: prospective study.

OBJECTIVES: To assess the quality of anaesthetic services as defined in the six anaesthetic clinical indicators against preset standards and to identify risk factors for adverse events in the recovery room. DESIGN: Prospective study. SETTING: All public hospitals providing anaesthetic care in Hong Kong. PATIENTS: Eighteen thousand, seven hundred and fifty-nine patients receiving elective or emergency anaesthesia administered by anaesthetists from June 1998 to July 1998. MAIN OUTCOME MEASURES: Patient demographics, American Society of Anesthesiologists status, category and nature of operation, presence of preoperative anaesthetic visit in ward, type of anaesthesia, reasons for a recovery room stay of more than a 2-hour duration, intubation to relieve respiratory distress in the recovery room, presence of hypothermia in the recovery room for operations lasting more than 2 hours, and dental or ocular injuries attributable to anaesthesia. RESULTS: There are two major findings from this study. Firstly, a high incidence of hypothermia in the recovery room was reported. Secondly, a greater risk of prolonged stay in the recovery room was identified for patients older than 65 years, major operations, and anaesthetic techniques using combined general and regional anaesthesia. CONCLUSION: The six anaesthetic clinical indicators reflected the provision of anaesthetic care in public hospitals in Hong Kong. Good compliance to the preset standard of the anaesthetic clinical indicators was achieved during the study period.

Adolescent↗

Serum modulates the intracellular calcium response of primary cultured bone cells to shear flow.

We investigated the effect of newborn bovine serum on the intracellular calcium [Ca(2+)](i) response of primary cultured bone cells stimulated by fluid flow. As it has been previously established that these cells exhibit [Ca(2+)](i) responses to fluid flow shear stress in saline media without growth factors or other chemically stimulatory factors, we hypothesized that the addition of serum to the flow medium would enhance the mechanosensitivity of the cells. We examined the effect of a short-term (10-15min) exposure of the cells to 2 and 10% serum prior to flow stimulation (pretreated) compared to not exposing the cells prior to flow stimulation (unpretreated). The cells were subjected to a well-defined, 90-s flow stimulus with shear stress levels ranging from 0.02 to 3.5Pa in a laminar flow chamber using a saline medium supplemented with 2 or 10% serum. For pretreatment, the serum concentration was the same from pre-flow to flow exposure. We observed a differential effect in the magnitude of the peak [Ca(2+)](i) response modulated by the concentration of serum in the pre-flow medium. Additionally, ATP-supplemented flow was examined as a comparison to the serum-supplemented flow and exhibited a similar trend in the peak [Ca(2+)](i) flow response that was dependent on ATP concentration and pre-flow exposure conditions. These findings demonstrate that under the conditions of this study, chemical agonist exposure can modulate the [Ca(2+)](i) response in bone cells subjected to fluid flow-induced shear stress.

Adenosine Triphosphate↗

Mitogen-activated protein kinase signaling in bovine articular chondrocytes in response to fluid flow does not require calcium mobilization.

In the present study, the role of mitogen-activated protein kinases (MAPKs) in chondrocyte mechanotransduction was investigated. We hypothesized that MAPKs participate in fluid flow-induced chondrocyte mechanotransduction. To test our hypothesis, we studied cultured chondrocytes subjected to a well-defined mechanical stimulus generated with a laminar flow chamber. The extracellular signal-regulated kinases 1 and 2 (ERK1/2) were activated 1.6-3-fold after 5-15 min of fluid flow exposure corresponding to a chamber wall shear stress of 1.6 Pa. Activation of ERK1/2 was observed in the presence of both 10% FBS and 0.1% BSA, suggesting that the flow effects do not require serum agonists. Treatment with thapsigargin or EGTA had no significant effect on the ERK1/2 activation response to flow, suggesting that Ca2+ mobilization is not required for this response. To assess downstream effects of the activated MAPKs on transcription, flow studies were performed using chondrocytes transfected with a chimeric luciferase construct containing 2.4 kb of the promoter region along with exon 1 of the human aggrecan gene. Two-hour exposure of transfected chondrocytes to fluid flow significantly decreased aggrecan promoter activity by 40%. This response was blocked by treatment of chondrocytes with the MEK-1 inhibitor PD98059. These findings demonstrate that, under the conditions of the present study, fluid flow-induced signals activate the MEK-1/ERK signaling pathway in articular chondrocytes, leading to down-regulation of expression of the aggrecan gene.

Aggrecans↗

Functional tissue engineering of articular cartilage through dynamic loading of chondrocyte-seeded agarose gels.

Due to its avascular nature, articular cartilage exhibits a very limited capacity to regenerate and to repair. Although much of the tissue-engineered cartilage in existence has been successful in mimicking the morphological and biochemical appearance of hyaline cartilage, it is generally mechanically inferior to the natural tissue. In this study, we tested the hypothesis that the application of dynamic deformational loading at physiological strain levels enhances chondrocyte matrix elaboration in cell-seeded agarose scaffolds to produce a more functional engineered tissue construct than in free swelling controls. A custom-designed bioreactor was used to load cell-seeded agarose disks dynamically in unconfined compression with a peak-to-peak compressive strain amplitude of 10 percent, at a frequency of 1 Hz, 3 x (1 hour on, 1 hour off)/day, 5 days/week for 4 weeks. Results demonstrated that dynamically loaded disks yielded a sixfold increase in the equilibrium aggregate modulus over free swelling controls after 28 days of loading (100 +/- 16 kPa versus 15 +/- 8 kPa, p < 0.0001). This represented a 21-fold increase over the equilibrium modulus of day 0 (4.8 +/- 2.3 kPa). Sulfated glycosaminoglycan content and hydroxyproline content was also found to be greater in dynamically loaded disks compared to free swelling controls at day 21 (p < 0.0001 and p = 0.002, respectively).

Animals↗

Chondrocyte translocation response to direct current electric fields.

Using a custom galvanotaxis chamber and time-lapse digital video microscopy, we report the novel observation that cultured chondrocytes exhibit cathodal migration when subjected to applied direct current (DC) electric fields as low as 0.8 V/cm. The response was dose-dependent for field strengths greater than 4 V/cm. Cell migration appeared to be an active process with extension of cytoplasmic processes in the direction of movement. In some cells, field application for greater than an hour induced elongation of initially round cells accompanied by perpendicular alignment of the long axis with respect to the applied field. Antagonists of the inositol phospholipid pathway, U-73122 and neomycin, were able to inhibit cathodal migration. Cell migration toward the cathode did not require the presence of serum during field application. However, the directed velocity was nearly threefold greater in studies performed with serum. Studies performed at physiologic temperatures (approximately 37 degrees C) revealed a twofold enhancement in migration speed compared to similar studies at room temperature (approximately 25 degrees C). Findings from the present study may help to elucidate basic mechanisms that mediate chondrocyte migration and substrate attachment. Since chondrocyte migration has been implicated in cartilage healing, the ability to direct chondrocyte movement has the potential to impact strategies for addressing cartilage healing/repair and for development of cartilage substitutes.

Animals↗

The extracellular matrix, interstitial fluid and ions as a mechanical signal transducer in articular cartilage.

OBJECTIVE: (1) Provide an overview of the biomechanical factors that are required to analyze and interpret biological data from explant experiments; (2) Present a description of some of the mechano-electrochemical events which occur in cartilage explants during loading. DESIGN: A thorough and provocative discussion on the effects of loading on articular cartilage will be presented. Five simplest loading cases are considered: hydrostatic pressure, osmotic pressure, permeation (pressure loading), confined compression and unconfined compression. Details of how such surface loadings are converted or transduced by the extracellular matrix (ECM) to pressure, fluid, solute and ion flows, deformation and electrical fields are discussed. RESULTS: Similarities and differences in these quantities for the five types of loading are specifically noted. For example, it is noted that there is no practical mechanical loading condition that can be achieved in the laboratory to produce effects that are equal to the effects of osmotic pressure loading within the ECM. Some counter-intuitive effects from these loadings are also described. Further, the significance of flow-induced compression of the ECM is emphasized, since this frictional drag effect is likely to be one of the major effects of fluid flow through the porous-permeable ECM. Streaming potentials arising from the flow of ions past the fixed charges of the ECM are discussed in relation to the flow-induced compaction effect as well. CONCLUSION: Understanding the differences among these explant loading cases is important; it will help to provide greater insights to the mechano-electrochemical events which mediate metabolic responses of chondrocytes in explant loading experiments.

Biomechanical Phenomena↗

Evaluation of the use of a platelet-counting tool in plateletpheresis.

OBJECTIVE: For years, blood transfusion centers in Taiwan have used the Quantitative Buffy Coat (QBC(R)) Hematology System for platelet counts on capillary blood samples in the laboratory screening of apheresis donors. The system has not been evaluated for the prediction of yields in plateletpheresis. Methods : The QBC instrument was evaluated for reproducibility of platelet counts and compared with five electronic cell counters. We also collected both capillary and venous blood from voluntary donors before donation and counted platelets, comparing the QBC system and an electronic blood cell counter (Sysmex K1000). The correlation between donors' predonation platelet counts and plateletpheresis yields was analyzed. RESULTS: The R values for platelet counts between the QBC Hematology System and other electronic counters are lower (0.759-0. 890) than among the electronic counters (0.929-0.973). The mean capillary platelet count and the mean venous platelet count were 241. 9+/-50.3x10(3)/microl and 233.2 +/-47.9x10(3)/microl by the QBC system, and 244.9+/-54.1x10(3)/microl and 218.9+/-46.5x10(3)/microl by the Sysmex K1000, respectively. Linear regression analysis showed that platelet yields correlated well with donors' predonation platelet counts using the Sysmex K1000 counter (R = 0.777- 0.890, p<0.001), but not with the QBC system (R = 0.326 approximately 0.755, p<0.05). CONCLUSION: The QBC Hematology System is not accurate enough to determine predonation platelet counts that are to be used for calculating the number of processing cycles for plateletpheresis.

Electronics↗

Prevalence and prediction of difficult intubation in Chinese women.

We conducted a prospective, blind observational study to investigate the prevalence and prediction of difficult intubation in Chinese women. Two groups of Chinese women were studied (151 pregnant and 260 non-pregnant). The prevalence of difficult intubation was 1.99% in the pregnant and 1.54% in the non-pregnant group. The difference was not statistically significant. Predictive variables for difficult intubation, including modified Mallampati class, thyromental distance and atlanto-occipital extension, had high sensitivity but low positive predictive value when used alone. A shorter thyromental distance had to be used as the criterion for prediction in Chinese women. Combination of predictive variables could improve the positive predictive value.

Adult↗

Radial nerve injury after intravenous cannulation at the wrist--a case report.

Peripheral venous cannulation is one of the commonest procedures performed in hospitals. The dorso-lateral aspect of the wrist is one of the favourite sites. Radial nerve injury, though extremely rare, can be a serious complication and has been reported twice. One patient was left with a permanent work disability due to a painful neuroma. Another patient required surgical intervention to remove a neuroma six months after the initial venous cannulation resulting in almost complete recovery. We report the first case of injury to the radial nerve at the wrist as a complication of venous cannulation where complete recovery occurred spontaneously. In our case, immediate removal of the cannula may be responsible for the improved outcome.

Adult↗

Intracellular calcium response of ACL and MCL ligament fibroblasts to fluid-induced shear stress.

This study examines the real-time intracellular calcium concentration, [Ca2+]i, response of canine medial collateral ligament (MCL) and anterior cruciate ligament (ACL) fibroblasts subjected to a fluid-induced shear stress of 25 dynes/cm2. In experiments using a modified Hanks' Balanced Salt Solution (HBSS) perfusate, both cell types demonstrated a significant increase in peak [Ca2+]i compared to respective no-flow controls, the response of MCL fibroblasts being nearly 2-fold greater than that of ACL fibroblasts. In studies where the cells were bathed in a medium of HBSS supplemented with 2% newborn bovine serum (NBS) and then introduced to flow with the same medium, ACL fibroblasts responded nearly 3-fold greater than MCL fibroblasts. Neomycin (10 mM), thapsigarigin (1 microM) and Ca(2+)-free media supplemented with EGTA (1 mM) were able to inhibit significantly the [Ca2+]i response to flow with HBSS in both fibroblasts. Thapsigargin also blocked the NBS flow response in both cell types, while neomycin and Ca(2+)-free media significantly inhibited the ACL response. Our findings demonstrate that ACL and MCL cells are not the same. These differences may be related to the disparate healing capacity of the ACL and MCL observed clinically.

Animals↗

Extracellular ATP modulates [Ca2+]i in retinoic acid-treated embryonic chondrocytes.

When treated with low doses of retinoic acid (RA), cephalic chondrocytes of the chick embryonic sternum mature and express phenotypic characteristics of postmitotic hypertrophic cells. In concert with these maturation-dependent changes, cells release adenine nucleotides into the culture medium. To ascertain if these compounds modulate chondrocyte function, we challenged chondrocytes with nucleotides and measured one determinant of the signal transduction pathway, intracellular Ca2+ concentration ([Ca2+]i). In the presence of micromolar concentrations of ATP, there was a dose-dependent elevation in chondrocyte [Ca2+]i; ADP caused a small but significant rise in the peak [Ca2+]i response. We found that the change in the [Ca2+]i response is linked to retinoid-dependent maturation of chondrocytes. Thus the [Ca2+]i rise was dependent on the RA concentration and treatment time. Immature caudal chondrocytes, cells that were not affected by RA, were used as control cells for this study. When treated with ATP, these cells did not exhibit a [Ca2+]i response. Although the purinergic subtype receptor was not characterized, the observation that cells responded to ATP and ADP but were refractory to AMP and adenosine suggested that P2 purinoceptors were expressed by chondrocytes. Because, during the same culture period, chondrocytes exhibited many of the unique characteristics of the terminally differentiated cell, the acquisition of purinergic receptors represents a new feature associated with expression of the mature phenotype. Finally, to ascertain if the ATP-dependent response was due to release of Ca2+ from intracellular stores, cells were treated with thapsigargin. Since this compound significantly reduced the [Ca2+]i signal, we concluded that the ATP response is mediated by release of cation, from the endoplasmic reticulum.

Adenosine Diphosphate↗

The effectiveness of systematic stroke care.

A coordinated, multidisciplinary approach had been applied to enhance the effectiveness of stroke care with varying enthusiasm; however, the effectiveness of this kind of stroke treatment model was noted in many studies. This study was designed to measure the effectiveness of systematic stroke management on the physical-functional outcome in terms of Activities of Daily Living (ADLs) scores. The higher the ADLs score, the higher the degree of physical disability, i.e., the higher the degree of dependence. Eighty-six stroke patients from the Department of Neurology in a medical center, and 88 stroke patients from the Department of Medicine in a local hospital were followed from the admission day to the discharged date. The effectiveness of stroke care in each hospital was measured by the comparisons between ADLs scores at discharge and ADLs scores at admission. Two-sample tests show that demographic characteristics, length of stay, average time elapsed since the occurrent stroke, number of families in caregiving, and ADLs scores at admission and at discharge did not differ much between these two groups. The improved ADLs scores for stroke patients treated in the Department of Neurology of the medical center were changed from the 14.1 +/- 4.9 at admission to 12.1 +/- 5.2 at discharge, and the changes of ADLs scores for patients treated in the Department of Medicine of the regional hospital was from 12.8 +/- 5.1 to 12.3 +/- 5.5 according to the degree of improvement. The significant finding was that the degree of improvement of ADLs scores for CVA patients from the medical center was significant (Wilcoxon Matched-Pairs Signed-Ranks Test, Z = -2.8, p < 0.01). Moreover, the degree of improvement of ADLs scores strongly differed between these two groups (Repeated measures of two-way ANOVA, F = 6.0, p < 0.05). The information presented here informs us that degree of physical-functional status of stroke patients should be improved because of the systematic stroke management.

Activities of Daily Living↗

What is the role of the convective current density in the real-time calcium response of cultured bone cells to fluid flow?

Cultured cells subjected to fluid flow are exposed to mechanical forces and electrokinetic forces. The convective current establishes an electrokinetic force created by the flow-dependent transport of mobile ions in the media over the charged cell surfaces. This current can be expressed as a current density, the current normalized by the cross-sectional area in which it exists. In this study, we hypothesized that the convective current density has no role in the bone cell real-time intracellular calcium response to fluid flow. Our hypothesis was tested by incorporating electrokinetic measurements and classical electrokinetic double-layer theory to estimate the value of convective current density in a parallel-plate flow chamber and then to apply an external current during the presence of fluid flow that would alter convective current density. There was no difference between the mean peak calcium response of cells exposed to flow with an altered (canceled or doubled) convective current density versus flow with an unmodified convective current density, as was measured with fura-2 fluorescence microscopy. These results suggest that mechanical forces, such as fluid-induced shear stress, rather than concomitant electrokinetic forces are the primary stimuli in eliciting the observed calcium response of bone cells to fluid flow.

Analysis of Variance↗

Intracellular Ca2+ stores and extracellular Ca2+ are required in the real-time Ca2+ response of bone cells experiencing fluid flow.

In this study, we sought to determine if there is a requirement for calcium entry from the extracellular space as well as calcium from intracellular stores to produce real-time intracellular calcium responses in cultured bone cells subjected to fluid flow. Understanding calcium cell signaling may help to elucidate the biophysical transduction mechanism(s) mediating the conversion of fluid flow to a cellular signal. An experimental design which utilized a scheme of pharmacological blockers was employed to distinguish between the biochemical pathways involved in this cell signaling. A parallel-plate flow chamber served as the cell stimulating apparatus and a fluorescence microscopy system using the calcium-sensitive dye fura-2 measured the intracellular calcium changes. In the present study, evidence for a role by the inositol-phospholipid biochemical pathway, specifically inositol trisphosphate (IP3) was obtained using neomycin which completely inhibited the calcium response to flow. Additionally, a concomitant role of extracellular calcium was demonstrated through experiments performed in calcium-free medium which also eliminated the flow response. Experiments conducted with gadolinium, a stretch-activated channel blocker, partially inhibited (approximately 30%) the flow response while verapamil, a type-L voltage sensitive channel blocker, had no effect on the flow response. These results suggest a requirement of extracellular calcium (or calcium influx) as well as IP3-induced calcium release from intracellular stores for generating the intracellular calcium response to flow in bone cells.

Analysis of Variance↗

Real-time calcium response of cultured bone cells to fluid flow.

Using a parallel-plate flow chamber and fura-2 fluorescence microscopy, intracellular calcium was measured cell by cell in preconfluent primary culture rat calvarial bone cells to 18, 35, and 70 dynes/cm2 of fluid-induced shear stress. A heterogeneous response with respect to peak amplitude and latency was observed for the culture, with an overriding dose-dependent relationship between the mean peak amplitude of response and shear-stress magnitude. A dose dependence was observed between the number of responsive cells (responding > 50% over basal levels) and shear-stress magnitude. Not all cells could be restimulated by repeated exposure to flow. The observed cell response appears to be independent of whether cells are clustered together or isolated. Substratum stretch, hydrostatic pressure, and fluid shear stress have been shown in the literature to increase inositol phosphate (IP3) in bone cells, with IP3 causing the release of calcium from intracellular stores such as the endoplasmic reticulum. Therefore, a 6-fold inhibitory effect observed when calcium release from stores was blocked with 8-(n,N-diethylamino)octyl 1-3,4,5-atrimethoxybenzoate hydrochloride implicates an IP3 biochemical pathway mediating the fluid flow response in bone cells.

Animals↗

The subjective assessment and pressure-flow study of outcome of surgical treatment for patients with prostatism and high voiding pressure.

BACKGROUND: In 1992, the International Continence Society (ICS) began to conduct an international multicenter study to correlate the symptoms and urodynamics in patients with BPH. Our institute was invited to participate this ICS-BPH study, and the preliminary (phase I) results have revealed poor correlation between preoperative symptoms and parameters of the pressure-flow study. This phase II study continued the phase I ICS-BPH study to assess the changes of subjective symptoms and objective parameters of pressure-flow study before and after TURP. METHODS: Fifty-two patients with prostatism, aged from 56 to 80, were evaluated using the ICS-BPH questionnaire, free urine flow rate and pressure-flow study. According to the criteria of maximum urine flow rate (Qmax) 15 ml/sec and voiding intravesical pressure at Qmax (Pves at Qmax) 100 cm H2O, low flow-high pressure (LFHP) was proved in 20 patients (38%), high flow-high pressure (HFHP) in 22 (42%), low flow-low pressure (LFLP) in 3 (6%), and high flow-low pressure (HFLP) in 7 (14%). Transurethral resection of the prostate (TURP) was performed for 33 of 42 patients with high voiding pressure (LFHP and HFHP groups). RESULTS: The weight of the TURP specimen was 28 +/- 6.3 gm. Sixteen patients repeated the questionnaire and pressure-flow study 9.0 +/- 2.1 months after surgery. Both irritative and obstructive symptom scores decreased in 15 (94%) of the 16 patients (p < 0.001). The opening intravesical pressure (openPves) and Pves at Qmax improved from 136 +/- 34 and 124 +/- 30 cm H2O preoperatively to 89 +/- 25 and 94 +/- 22 cm H2O postoperatively respectively (p < 0.004). However, UFRmax, 16.7 +/- 6.0 ml/sec preoperatively and 19.3 +/- 6.4 postoperatively, showed no statistical difference. If the HFHP and LFHP groups were compared separately, the degree of improvement in symptomatology or parameters of pressure-flow study was similar, although changes in HFHP group appeared more evident. UFRmax in LFHP group changed significantly from 11.9 +/- 2.8 preoperatively to 22.1 +/- 6.7 ml/sec postoperatively. For the patients with high flow obstruction (HFHP group), although UFRmax did not increase after TURP, the symptom score, openPves and Pves at Qmax, decreased as much as the LFHP group did. CONCLUSIONS: Based on the analysis of the pressure flow study, TURP not only offers an advantage to the patient with classical obstruction (LFHP group), but also to patients with high flow obstruction (HFHP group). However, this does not suggest that a pressure-flow study should be performed routinely for a male with prostatism. It is advised only for patients with Qmax > 15 ml/sec but exhibiting typical symptoms.

Aged↗

A method for inducing equi-biaxial and uniform strains in elastomeric membranes used as cell substrates.

A device is described which is designed to bring about uniform and equi-biaxial strains of 0.04-0.4% on a circular elastomeric sheet upon which cells are grown in a monolayer. Strain measurements at six different radii of the well provide evidence of the uniformity of the strain field over the 2.54 cm diameter of the well with a mean strain of 0.15% and a standard deviation of 0.01% strain. Major advantages of the system over those previously described are that (1) the substrate remains in the same plane throughout the application of stretch, (2) the device is designed to provide a state of uniform equi-biaxial strain to the entire substrate of the cells and (3) all cells 'see' the same strain field, no matter what their orientation. This allows for real-time optical monitoring of the cells throughout the stretching cycle of the cell substrate. In this way, changes in the cell membrane, cell nucleus, cytoskeleton and in fluorescently labelled calcium can be monitored microscopically during application of an equi-biaxial mechanical stretch.

Biocompatible Materials↗