Biomedical subjects
Publications and source records attributed to C C Wong.
Each year at the Annual Scientific Meeting of the British Society for Haematology, there is a slide session in which microscopic slides of six patients with haematological disorders are discussed by two experts. Further data and the final diagnosis are then provided. The slide session is presented here, as it occurred at the meeting.
Pedicle screw system has increasingly been used for correction of thoracic scoliosis. It offers several biomechanical advantages over hook system as it controls all three-column of the spine with enhanced stability. Of many techniques of pedicle screw placement in the thoracic spine, the funnel technique has been used in Sarawak General Hospital since 2002. This prospective study aims to assess the accuracy of the placement of thoracic pedicle screws using the funnel technique in the corrective surgery of idiopathic scoliosis. A total of 88 thoracic pedicle screws were inserted into the T4 to T12 vertebrae of 11 patients. Post-operative CT-scan was performed to evaluate the position of the pedicle screw. Seventy six (86.4%) screws were noted to be totally within the pedicle. There was no screw with medial violation of the pedicle, 8 (9.1%) screws breeching the lateral wall of the pedicle and 4 (4.5%) screws with anterior and lateral penetration of the vertebral body. No clinical sequel with the mal-positioned screws was noted. In conclusion, the funnel technique enabled simple, accurate and reliable insertion of pedicle screw even in the scoliotic thoracic spine without the need of any imaging guidance. It is however imperative for the surgeon to have a thorough knowledge of the thoracic spine anatomy, and to be familiar with the technique to insert these screws diligently.
The direct photolysis and the photocatalytic degradations of dicamba in TiO2 suspensions with and without the use of hydrogen peroxide were studied using two different monochromatic UV irradiations (300 and 350 nm). Both the direct photolysis and photocatalytic degradations of dicamba follow pseudo-first-order decay kinetics. Photolysis reactions were slow but the corresponding photocatalysis rates were increased by about 3 and 5 times in the presence of TiO2 at 300 and 350 nm of UV, respectively. Photocatalytic rates were increased with the pH at acidic to neutral ranges because of the increase of hydroxide ions, but the reaction was gradually retarded at the alkaline medium due to the effect of charges repulsion. The different proton sources causing various degrees of rate retardation were due to the presence of the corresponding counter anions. The results of H2O2-assisted photocatalysis experiments showed that a low H2O2 dosage in photocatalysis using UV 300 nm would enhance the decay rate of dicamba by 2.4 times, but an overdose of H2O2 will retard the rate because of the expenditure of hydroxyl radicals. However, this process was found impracticable at UV 350 nm due to the absorption characteristic of H2O2. A neutral initial pH level was found to favour the H2O2-assisted photocatalysis at UV 300 nm. The reactions were highly retarded at the alkaline medium due to the unstable properties of H2O2.
Photocatalytic degradations of alachlor in TiO2 suspensions with and without the use of hydrogen peroxide were studied using two different monochromatic UV irradiations (300 and 350 nm). Direct photolysis of alachlor was a rather slow process, but the addition of TiO2 enhanced the reaction rates by 12 and 26 times using 300 and 350 nm UV irradiation, respectively. The results showed that a low H2O2 dosage in photocatalysis using 300 nm UV would enhance the rates by 3.3 times, but an overdose of H2O2 will retard the rate due to the hydroxyl radicals are consumed. However, this process is impracticable at 350 nm due to the absorption characteristic of H2O2. A neutral initial pH level was found to favor the H2O2 assisted photocatalysis at 300 nm UV illumination. Eleven major intermediates were identified by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) and MS/MS. The major degradation mechanisms of H2O2-assisted alachlor photocatalysis include dechlorination, dealkylation, hydroxylation, cyclization, scission of C-O bond, and N-dealkylation. Bell-shaped evolution profiles of different intermediates were observed. Degradation pathways were proposed accordingly to illustrate series of degradation steps. The TOC analysis revealed the different stages of the reaction.
The disappearance and modeling of the ozonation of 2,4,6-trichlorophenol (TCP) was studied under different initial TCP concentrations and initial pH levels. The ozonation of TCP was found to follow a pseudo-first-order reaction. The degradation rates increased with the initial pH, and decreased with initial TCP concentration. 2,6-Dichlorohydroquinone was identified as the major intermediate, indicating that dechlorination and hydroxylation co-occurred during TCP ozonation. A model was proposed to quantitatively predict the pseudo-first-order rate constants under different initial TCP concentration and different initial pH levels. The proposed model can successfully describe the reaction; therefore another practical equation was proposed to predict the TCP removal rate at any detention time, which has high potential for practical applications and reactor design.
Direct photolysis and photocatalytic degradations of alachlor, a widely used herbicide, were studied using three different monochromatic UV lamps (254, 300 and 350 nm) and two TiO(2) sources. Both the direct photolysis and photocatalytic degradations of alachlor follow pseudo-first-order decay kinetics. TiO(2)-P25 was found to be an effective photocatalyst compared to TiO(2)-BDH. The direct photolysis of alachlor was dominant at 254 nm even if TiO(2) was present in the solution. Among the three UV wavelengths used, the highest photocatalysis quantum yield was obtained at 300 nm. The photocatalytic degradation rate of alachlor increased with the dosages of TiO(2), but an overdose of TiO(2) would retard the reaction due to light attenuation. Photocatalytic reactions were slightly enhanced in an alkaline medium, and the different proton sources causing various degrees of rate retardation were due to the presence of the corresponding counter anions. This effect was diminished at a later stage after the reaction intermediates were formed.
The differential expression of cytochrome P4501A1 gene expression (CYP1A1) in liver, intestine and gill of juvenile tilapia following oral exposure to polychlorinated biphenyl (PCB) Aroclor-1254 or Aroclor-1260 spiked food were investigated. The fish was fed with 0.1 g/g of body weight each day of the spiked food with a concentration of approximately 8 ppm. Fish fed with betaNF- or acetone-spiked food were used as positive and negative controls, respectively. On day 1, 3 and 7 of post-treatment, the fish were sampled and analyzed for the total accumulated levels of PCBs, as well as the induced levels of CYP1A1 mRNA. Our results indicated that the fish fed with PCBs-spiked food showed a time-dependent bioaccumulation of PCBs. The time course studies also revealed that in the first 3 days of feeding, significant increases in CYP1A1 were found in intestine (betaNF: 320% and Aroclor-1260: 290%), followed by liver (betaNF: 144%, Aroclor-1260: 123% and Aroclor-1254: 110%). The transcript levels, then declined slowly. There was no induction of gill CYP1A1 mRNA expression in all treatment groups. Among all the tested tissues, the highest intestinal CYP1A1 transcripts induction has highlighted its prompt response to dietary PCBs exposure. Our study supported the important role of intestine in response to dietary PCBs exposure. In addition, in the present study the relative potency of Aroclor-1260 over Aroclor-1254 in stimulating CYP1A1 expression was discussed, indicating that the highly chlorinated PCBs had a higher potency of bioaccumulation and CYP1A1 mRNA induction.
Improvements in the overall treatment of patients with aggressive, large tumours involving the bone have made it possible to preserve and salvage limbs instead of amputating them. Each patient is unique in his clinical presentation and social circumstance. The different reconstructive options available allow us to choose the most appropriate method suited to the particular patient and with minimal delay, even when resources are limited. The patient and the relatives actively participate in the choice. The early experience of the different techniques for reconstructing these bone defects at our hospital are presented in this paper.
During critical periods of development, hypothyroidism causes abnormalities of the central nervous system such as incomplete maturation of neuronal and glial cells, reduction in synaptic densities and myelin deficits. In this study expression of development regulated genes, ie transcription of beta-actin, sema 3F, CRMP 1 to 4, GAP-43, G alpha o1, G alpha o2 and translation of beta-actin, G alpha o, G alpha o1, CRMP-2, CRMP-4 genes were examined in the hippocampus of neonatal methimazole induced hypothyroid rats at the age of day 16. All CRMPs mRNA levels were significantly higher in the hypothyroid rats. Significant higher CRMP-2 protein but not CRMP-4 protein was found in the hypothyroid rats. The neonatal experimental hypothyroid states did not affect the protein levels of beta-actin but up-regulate its mRNA. Transcription of CRMP 1 to 4, GAP-43, G alpha o1 but not G alpha o2 and sema 3F was altered by the neonatal treatment. The only sex difference in gene expression was found in the transcription of CRMP-2 gene.
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In this study, expressions of cell-cycle-related genes: p53, retinoblastoma (Rb), p21, bcl-2(alpha), bcl-2(beta); protooncogene c-ski; glial cell marker protein gene S100beta; neurotransmitter gene, substance P and sexual-differentiation-related genes, androgen receptor (AR) and estrogen receptor beta (ER(beta)), are studied in the olfactory bulb of groups of both six female and six male rats at the ages of 3, 10, 20 and 40 days. Expressions of housekeeping genes such as beta-actin, cyclophilin and proliferating cell nuclear antigens (PCNA) are determined using reverse transcription polymerase chain reaction (RT-PCR) for the correction of unequal amount of cDNA added into the samples. Using labeled 32P-dCTP and Phosphorimager technology, relative abundance of radioactivities of the PCR products is obtained by dividing the radioactivity of each individual sample by the corresponding radioactivities of different housekeeping genes. Data evaluated by Two-way ANOVA indicate that only the bcl-2(alpha) gene expression is affected significantly by age, sex and their interactions no matter which of the three housekeeping genes is used for correction. When beta-actin was used for corrections, effects of age but not sex were found in the expressions of p53, Rb, p21, AR, ER(beta), substance P and S100beta genes, but not in bcl-2(beta), c-ski, cyclophilin and PCNA genes. While cyclophilin was used for corrections, only the p53, Rb, AR, ER(beta), substance P and S100beta but not the bcl-2(beta), p21, c-ski, PCNA and beta-actin genes are affected by age. They are all not influenced by sex of the animals. Only the AR, ER(beta) and S100beta genes are age-dependent when PCNA was used for the correction. The other gene expressions are not altered by sex, while the interactions of age and sex were found to be significantly affecting the bcl-2(beta) gene expression. Conclusively, developmental changes of the p53, Rb, AR, ER(beta), substance P and S100beta genes expressions are quite evidenced while only the bcl-2(alpha) gene seems to change significantly during the sexual differentiation of olfactory bulb in rats.
Reverse transcription-polymerase chain reaction using 32P-labeled dCTP with specific primers for putative neurotransmitters related and neuronal growth-related genes (GAP-43, NGF and BDNF) were used to search for evidence of such substances in the Merkel cell. Merkel cell samples were made from sinus hairs in the facial skin of rats. The relative amount of mRNA in a tissue sample concentrated in Merkel cells was compared semiquantitatively to that from nearby tissue without Merkel cells. mRNAs for VIP, tyrosine hydroxylase, substance P were found in higher concentration in Merkel cells than in control tissues. mRNA for genes encoding pro-enkephalin, GAP-43, CGRP, NGF and BDNF were detected in the Merkel cell samples at concentration statistically equivalent to those found in the control tissues. It was concluded that the relative concentration of mRNAs for VIP, tyrosine hydroxylase and substance P is consistent with the possibility that Merkel cell acts as a possible transduction element in mechanical excitation of sense organs in which Merkel cells are present.
In this study we investigate the influence of Hepatocyte Growth Factor (HGF) on the motility of embryonic forelimb myoblasts. Using Blindwell chemotactic chambers, it was found that HGF at concentrations of 1-50 ng/ml dramatically enhanced the ability of myogenic cells to migrate. This stimulatory effect was elicited in a dose-dependent fashion and the effect was reversed with the addition of HGF neutralizing antibodies. A checkerboard analysis was performed and it revealed that HGF's effect on limb myoblast motility was through both chemokinesis and chemotaxis. HGF was also examined for its ability to stimulate myogenic cell proliferation, using MF20 antibody as the myogenic marker. At all concentrations tested, HGF did not stimulate an overall increase in the numbers of MF20-positive myoblasts in culture. To examine the chemokinetic effect of HGF on cell migration in the limb, cells were isolated from the proximal regions of the limb (areas rich in myogenic cells), exposed to HGF, labeled with DiI and transplanted into 11.5 day mouse forelimbs. After 36 h of culture, it was found that DiI-labeled limb cells, pretreated with HGF, migrated significantly further in the limb than labeled cells that have not been exposed to HGF. The chemotactic effect of HGF was also investigated by implanting beads loaded with and without HGF into the 11.5 day limb. Proximal to the beads, DiI-labeled limb cells were also transplanted. It was found that HGF was able to chemotactically attract and direct the migration of DiI-labeled limb cells. Immunohistological staining was performed with HGF antibodies to determine the distribution of HGF in the 11.5 day mouse forelimb. It was found that HGF was strongly expressed by the apical ectodermal ridge (AER), the ectoderm and the mesenchyme directly beneath the AER. Positive staining was also obtained for the myogenic regions. However, the pattern was heterogeneous--punctuated with myogenic cells expressing and not expressing HGF.
The purpose of this study was to determine the suitability of alpha-aminoisobutyric acid (AIB) as a marker of the integrity of the blood-brain barrier (BBB) during studies in which amino acid content in dialysates collected by microdialysis probes and behavior of the rat are studied concurrently. AIB (200 mg/kg) was injected intraperitoneally at 1800 h into 24-h fasted, ketamine-acepromazine anesthetized rats on either 10 or 30 days following guide cannula implantation. Dialysates from the medial preoptic area and blood from the tail vein were collected 1 h before and after the AIB injection. Analysis of amino acids, including AIB, in the collections was conducted by reverse-phase HPLC. In 21 of 24 rats, AIB in dialysates averaged less than 3% of plasma at 10, 30, and 50 min after AIB injection. In those rats unidirectional blood-to-brain transfer constant, K(i), of AIB was constant and a good relationship was found between dialysate amino acid concentrations and those predicted from calculations of transport based on the brain uptake index (BUI) for some amino acids. AIB concentration in dialysates was greater than 10% of plasma at 30 min in only 3 of 24 rats. We conclude that AIB can be used as a marker to monitor the integrity of the BBB during serial measurements of dialysate concentrations of amino acids and has application in behavioral studies.
Testin is a testosterone-responsive Sertoli cell secretory product. In the present study, we demonstrated that the amount of testin secreted by Sertoli cells in vitro was comparable with several other Sertoli cell secretory products. However, virtually no testin was found in the luminal fluid and cytosols of the testis and epididymis when the intercellular junctions were not previously disrupted, suggesting that secreted testin may be reabsorbed by testicular cells in vivo. Studies using Sertoli cells with and without a cell surface cross-linker and radioiodination in conjunction with immunoprecipitation illustrated the presence of two polypeptides of 28 and 45 kDa, which constitute a binding protein complex that anchors testin onto the cell surface. The 28- and 45-kDa peptide appear to be residing on and inside the cell surface, respectively. Immunogold EM studies illustrated testin was abundantly localized on the Sertoli cell side of the ectoplasmic specialization (a modified adherens junction) surrounding developing spermatids. In contrast, very few testin gold particles were found at the site of inter-Sertoli tight junctions. When the inter-Sertoli tight junctions were formed or disrupted, no significant change in testin expression was noted. This is in sharp contrast to the disruption of Sertoli-germ cell junctions, which is accompanied by a surge in testin expression. These results demonstrate the usefulness of testin in examining Sertoli-germ cell interactions.
BACKGROUND: Although long-term beta-blocker therapy has been found beneficial in patients after an acute myocardial infarction, these drugs are greatly underused by clinicians. Moreover, the dosages of beta-blockers used in randomized controlled trials appear to be much larger than those routinely prescribed. OBJECTIVE: To determine whether an association exists between the dosage of beta-blockers prescribed after a myocardial infarction and cardiac mortality. METHODS: We performed a retrospective cohort study of 1165 patients who survived an acute myocardial infarction from January 1, 1990, through December 31, 1992. These patients represent a subgroup of the 6851 patients hospitalized at northern California Kaiser Permanente hospitals. RESULTS: Of the 37.7% of patients prescribed beta-blocker therapy, 48.1% were treated with dosages less than 50% of the dosage found to be effective in preventing cardiac death in large randomized clinical trials (lower-dosage therapy). Compared with patients not receiving beta-blockers, those treated with lower-dosage therapy appeared to have a greater reduction in cardiovascular mortality (hazard ratio, 0.33; P=.009) than patients treated with a higher dosage (hazard ratio, 0.82; P=0.51), after adjustment for age, sex, race, disease severity, and comorbidities. CONCLUSIONS: The dosages of beta-blockers shown to be effective in randomized trials are not commonly used in clinical practice, and treatment with lower dosages of beta-blockers was associated with at least as great a reduction in mortality as treatment with higher dosages. This suggests that physicians who are reluctant to prescribe beta-blockers because of the relatively large dosages used in the large prospective clinical trials should be encouraged to prescribe smaller dosages.
OBJECTIVES: The goal of this study was to examine sex differences in the use of coronary angiography after acute myocardial infarction in managed care facilities by using the American College of Cardiology/American Heart Association (ACC/AHA) practice guidelines (which incorporate clinical information on infarct complications, severity of illness, and comorbidity). BACKGROUND: Although sex differences in the use of coronary angiography after acute myocardial infarction have been previously explored, the effects of indications for coronary angiography and common health insurance coverage on the sex and coronary angiography use relation have not been previously examined. METHODS: This historical prospective study analyzed data collected from a random sample of 1133 patients (377 women, 756 men) from among 2740 patients hospitalized with validated acute myocardial infarction between Jan. 1, 1990, and Dec. 31, 1992, from seven of 16 Northern California Kaiser Facilities (three with high procedure rates for coronary angiography, four with low rates relative to the average region-wide utilization rate). In accordance with the guidelines, use of coronary angiography was determined for the in-hospital and "0 to 8 weeks" postdischarge periods. Patients were assigned time specific ACC/AHA classes for coronary angiography indications (I = highly indicated, IIA = probably indicated, IIB = not harmful, III = not indicated). The independent impact of ACC/AHA class, age, race, and facility on the sex and use of coronary angiography relation was examined by the Cox proportional hazard model. RESULTS: Accounting only for ACC/AHA class, fewer women underwent coronary angiography compared with men among the "highly indicated" class I patients during the in-hospital period (43% vs 35%; p < 0.05), but not after discharge. Use of coronary angiography between the sexes was not statistically different among classes IIA, IIB, and III for both periods. After adjusting for differences in age, race, facility, and ACC/AHA class, we found no sex difference in in-hospital use of coronary angiography (hazard ratio (HR) = 1.02; 95% confidence interval [CI], 0.82 to 1.26), but among those discharged without receiving coronary angiography, women probably received fewer angiograms than did men (HR = 0.61; 95% CI, 0.37 to 1.00). For both periods, no significant sex difference in use of coronary angiography was found within ACC/AHA classes after adjustments. CONCLUSION: In a setting where health insurance is prepaid and after controlling for ACC/AHA classification for coronary angiography indications, age, race, and facility, use of coronary angiography after myocardial infarction was similar among men and women during hospitalization, but was lower among women after discharge. Likely explanations for these differences in use of coronary angiography may include effects of physician judgment, patient decision, other social factors, or clinical information not captured in the practice guidelines.
BACKGROUND: This study was undertaken to study gender differences in the use of coronary angiography (CA), revascularization (RV), and cardiovascular disease (CVD) mortality in patient with acute myocardial infarction (AMI) who were assigned to "High Indication for CA" per the American College of Cardiology/American Heart Association (ACC/ AHA) practice guidelines. METHODS AND RESULTS: This is a historical prospective study based on a stratified random sample of 1165 AMI patients from January 1990 to December 1992 at seven health maintenance organization hospitals. CA was highly indicated in 286 women and 564 men. In a Cox hazard ratio (HR), women received significantly (P<.05) fewer CAs (HR, .78) and RVs (HR, .62) than men after adjusting for age, Charlson index, and congestive heart failure. Crude CVD mortality for women was higher than men (HR, 1.7). After adjustments for age, Charlson index, and congestive heart failure, the HR was reduced to 1.19 for women. Further adjustment for CA and RV lowered CVD mortality in women slightly (HR, 1.14). RV is associated with lowered CVD (HR, .41). CONCLUSIONS: In patients with high indication for CA, use of CA and RV was significantly lower in women. After adjustments were made for risk profile and treatment modalities, women did not have a significantly increased risk for CVD compared with men. However, the apparent protective effect of RV in patients with a high indication for CA suggests that practices in line with ACC/AHA guidelines may reduce CVD in both women and men.