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Biomedical subjects

P T Chan

Publications and source records attributed to P T Chan.

At least 19 recordsLinked to original sources
PubMed2002

Internal fixation of valgus-impacted humeral head fractures using the screw-wiring technique.

Between February 1996 and July 2000 eight patients (ages 35-74 years) with nine severely impacted humeral head fractures were operated on with the aim of preserving the humeral heads. Patients were treated surgically with open reduction, autologous bone grafting, and internal fixation with a screw-wiring technique. There were no complications and all patients were satisfied with the results. After 10-63 months there was no evidence of nonunion, arthritis, avascular necrosis, or loosening of implants. The mean Constant score was 83 (66-97) points. Results of this study support the observation that four-part valgus-impacted humeral head fractures without significant lateral displacement have a low incidence of avascular necrosis.

Adult↗
PubMed2001

Testicular sperm extraction combined with intracytoplasmic sperm injection in the treatment of men with persistent azoospermia postchemotherapy.

BACKGROUND: Men who remain azoospermic long after undergoing chemotherapy have generally been considered sterile. The authors report their experience with testicular sperm extraction (TESE) combined with intracytoplasmic sperm injection (ICSI) applied to azoospermic men who previously received chemotherapy for a variety of indications. METHODS: Among 231 cycles in 198 patients who underwent TESE-ICSI for nonobstructive azoospermia from 1995 to 2000, 20 TESE procedures in 17 patients who previously received chemotherapy were identified. All TESE procedures were performed with microsurgical control under local anesthesia with sedation or general anesthesia. The pretreatment hormonal profile, histology of testicular biopsies, and outcomes of TESE-ICSI in this subgroup of patients were analyzed. RESULTS: The mean patient age was 37.4 years (range, 28-54 years), and the mean follicle-stimulating hormone level was 21.8 mIU/mL (range, 7.1-43.1 mIU/mL). The mean age for female partners was 33.5 years (range, 22-43 years). Six patients had received chemotherapy for Hodgkin lymphoma (34%), four patients had received chemotherapy for testicular neoplasm (24%), two patients had received chemotherapy for non-Hodgkin lymphoma (12%), two patients had received chemotherapy for leukemia (12%), one patient had received chemotherapy for Wilms tumor (6%), one patient had received chemotherapy for mediastinal germ cell tumor (6%), and one patient had received chemotherapy for nephrotic syndrome (6%). Three patients (18%) received additional radiation therapy. The mean interval from chemotherapy to TESE was 16.3 years (range, 6-34 years). All patients had at least two semen analyses to confirm azoospermia. A total of 20 attempts of TESE-ICSI were performed (mean, 1.2 attempts per patient). Testicular histology revealed Sertoli cell-only pattern in 76% of patients. The remaining 24% of patients had hypospermatogenesis as their most advanced spermatogenic pattern. Among the men with Sertoli cell-only pattern, 23% had sperm retrieved by TESE. Sperm retrieval was accomplished in 9 of 20 attempts (45%), with biochemical pregnancy after sperm retrieval in 4 of 9 couples (45%) and clinical pregnancy in 3 of 9 couples (33%). Live deliveries were achieved in 2 of 9 couples (22%). Two healthy boys and one girl were delivered. No correlation was noted between the outcome of TESE-ICSI and the underlying conditions that were treated with chemotherapy nor with the chemotherapeutic agents used. CONCLUSIONS: Using TESE-ICSI, sperm retrieval leading to pregnancy and the delivery of healthy children is possible for men with long-standing azoospermia after chemotherapy. The prognosis for sperm retrieval was not influenced clearly by the chemotherapy regimen or the disease treated. Diagnostic biopsy also was of limited value in predicting the outcome of sperm retrieval. Despite prolonged nonobstructive azoospermia after undergoing chemotherapy, men no longer should be considered sterile in the era of advanced assisted reproductive techniques.

Adult↗
PubMed2001

FGF-2 immunoreactivity in adult rat ependyma and choroid plexus: responses to global forebrain ischemia and intraventricular FGF-2.

Fibroblast growth factor 2 (FGF-2) immunoreactivity (IR) was examined in the ependyma and choroid plexus (CP) of lateral and third ventricles in normal adult rats, as well as in response to transient forebrain ischemia (TFI) and exogenous FGF-2 delivered intraventricularly for several days by osmotic pump. Similar patterns of FGF-2 IR were seen in the CP epithelia of both lateral and third ventricles, as well as in ependymal cells of the third ventricle and along lateral sides of the lateral ventricles. Consistent staining was seen along the apical aspect of epithelial cells facing the cerebrospinal fluid (CSF). Cytoplasmic staining was seen in the absence of ischemia, and was dramatically reduced in response to TFI. FGF-2 treatment followed by TFI resulted in sustained FGF-2 IR within CP and ependymal cells, supporting the idea that these tissues are involved in synthesis and secretion of growth factors into the CSF. In contrast, along the medial sides of the lateral ventricles, adjacent to brain structures such as the hippocampus, consistent staining was seen along the basal aspect of the ependymal cells. We propose that at least some regions of ependyma may function to transport molecules such as FGF-2 directly into the underlying brain parenchyma.

Animals↗
PubMed2000

Short-term complications of pubovaginal sling procedure for genuine stress incontinence in women.

OBJECTIVES: To evaluate the complication rate intraoperatively and within the first 30 postoperative days of the pubovaginal sling procedure. METHODS: From January 1992 to September 1996, we prospectively analyzed 90 women with type II and III genuine stress incontinence (age 38 to 84 years, average Valsalva leak point pressure 57.5 cm H2O) who underwent the pubovaginal sling procedure at our institute. Sixty percent of patients had no previous surgical treatment for their incontinence. Thirty-three percent of our patients have significant comorbidity (chronic obstructive lung disease, diabetes, coronary artery disease, peripheral vascular disease). RESULTS: The complication rate within the first 30 postoperative days was 19%, which included pneumonia (1.1%), deep venous thrombosis (1.1%), urinary retention (3.3%), wound infection (7.7%), intraoperative bladder laceration (3.3%), urinary tract infection (1.1%), and superficial thrombophlebitis (1.1%). A similar complication rate was noted among our patients with no previous surgical treatment for their incontinence. CONCLUSIONS: The complication rate of our prospective series of pubovaginal sling procedures was comparable to that of the other surgical procedures for genuine stress incontinence reported in the literature. We conclude that even though the pubovaginal sling procedure is a relatively complex surgery, in view of its satisfactory long-term success rate reported in the recent literature, pubovaginal sling procedure should also be considered a primary surgical treatment for genuine stress incontinence in a selected population of women.

Adult↗
PubMed2000

Nonobstructive azoospermia.

Nonobstructive azoospermia (NOA) remains a challenging condition in reproductive medicine to manage. The genetic basis of NOA related to partial deletions of the Y-chromosome has been intensely investigated. Such information is of prognostic value and allows more insightful genetic counseling of couples who opt for assisted reproductive technology. Testicular sperm extraction (TESE) combined with intracytoplasmic sperm injection has allowed many men with NOA to father their own biologic children. Although studies in the current literature support open testicular biopsy as the most reliable method to obtain testicular sperm, less invasive techniques such as testicular fine-needle aspiration and percutaneous needle biopsy are feasible alternatives in selected groups of patients. Measures to improve the efficacy of TESE, including the application of microsurgical techniques, are addressed. Other recent developments related to the management of NOA reviewed include processing of testicular tissue, cryopreservation of retrieved spermatozoa, in-vitro maturation of germ cells and microinjection of immature spermatogenic precursor cells.

Humans↗
PubMed1999

Attitudes of Hong Kong high school students towards the nursing profession.

The increased development of hospital services in Hong Kong over the last decade has given rise in the demand for more recruits to join the nursing profession. Despite the advancement in education and the improvement in the working conditions, the problems of attracting sufficient new recruits remain critical. This study aimed to examine high school students' attitudes towards the nursing profession and to identify the contributing factors affecting shortage of nurses within the context of Hong Kong. A convenience sample of 375 high school students was recruited. A questionnaire was used to measure their knowledge, attitudes and intention to study nursing. Descriptive and inferential statistics were used to describe their career preferences and to compare knowledge, attitudes and intention scales between gender and nursing exposure groups. Results indicated that the students were generally knowledgeable about nursing but were reluctant to pursue nursing as a career. However, students who were socially acquainted with a nurse demonstrated a slightly more positive attitude towards nursing and slightly higher intention to pursue nursing as a career compared with those having no social acquaintance with a nurse. Implications for promotion of nursing profession and limitations of the study were discussed.

Adolescent↗
PubMed1999

Jasmine green tea epicatechins are hypolipidemic in hamsters (Mesocricetus auratus) fed a high fat diet.

These studies were designed to test the hypolipidemic activity of green tea epicatechins (GTE) isolated from jasmine green tea. In Experiment 1, three groups of hamsters were given a semisynthetic diet containing 200 g lard/kg and 1 g cholesterol/kg for 4 wk. The control group received distilled water, and the other two groups received either 15 g/L green tea water extract (GTWE) or 5.0 g/L GTE solution. Both the GTWE and GTE groups had lower concentrations of serum total cholesterol (TC) and triacylglycerols (TG) than the controls (P < 0.05). In Experiment 2, four groups of hamsters received tap water as the drinking fluid, but they were given the same high fat and cholesterol diet supplemented with 0 (control), 1.1, 3.4 or 5.7 g GTE/kg diet. The hypolipidemic effect of jasmine GTE was dose dependent. In Experiment 3, the time-course of changes in serum TC and TG was monitored in hamsters given the high fat diet supplemented with 5.7 g GTE/kg in comparison with that of controls. The hypolipidemic effects of dietary GTE were evident after feeding for 2 wk. Dietary supplementation of GTE did not affect liver fatty acid synthase. However, GTE-supplemented hamsters had higher fecal excretions of total fatty acids, neutral sterols and acidic sterols compared with the control group. In Experiment 4, hamsters were fed nonpurified diet; the control group drank distilled water, and the GTE group drank distilled water containing 5.0 g GTE/L. No differences in activities of 3-hydroxy-3-methyl glutaryl coenzyme A reductase and intestinal acyl CoA:cholesterol acyltransferase were observed. This study suggests that the hypolipidemic activity of GTE is not due to inhibition of synthesis of cholesterol or fatty acid but is most likely mediated by its influence on absorption of dietary fat and cholesterol.

Animals↗
PubMed1999

Socio-cultural perspectives on the image of nursing: the Hong Kong dimension.

Using structured interviews a study was undertaken with 19 high school students in Hong Kong to elicit their perceptions of nursing as a profession. The study also sought to gauge the extent of the students' intentions on pursuing a career in nursing. Responses were content analysed to determine the extent of knowledge and understanding held, intentions on choosing nursing as a career and their reasons. Findings suggest the image of nursing to be poor and that nursing as a career is far from desirable amongst the teenagers of Hong Kong. The reasons appear to be related to the notion of monetary rewards and status within the Hong Kong community. There is also a lack of knowledge as to what nurses do. The implications of such findings include the lost potential for recruitment of candidates of high calibre with a lot to offer the profession and their society. It suggests the need for the profession to find ways of publicizing and marketing the positive aspects with elements of realism which the general population in that part of the world could relate to more readily.

Adolescent↗
PubMed1998

Priapism secondary to penile metastasis: a report of two cases and a review of the literature.

Malignancy metastasis to the penis is an uncommon clinicopathological entity. We present two cases of malignant priapism following penile metastasis, in which the diagnosis was established by core needle biopsy of the corpus cavernosum. Primary tumors were urothelial carcinoma of the urinary bladder in one case (the patient having concomitant high-grade prostatic adenocarcinoma) and prostatic adenocarcinoma in the other. The clinicopathological features of 51 previously reported cases of penile metastasis in the recent literature are reviewed.

Adenocarcinoma↗
PubMed1998

Regulation of the collagenase-3 receptor and its role in intracellular ligand processing in rat osteoblastic cells.

We have previously described a specific, saturable receptor for rat collagenase-3 in the rat osteosarcoma cell line, UMR 106-01. Binding of rat collagenase-3 to this receptor is coupled to the internalization and eventual degradation of the enzyme and correlates with observed extracellular levels of the enzyme. In this study we have shown that decreased binding, internalization, and degradation of 125I-rat collagenase-3 were observed in cells after 24 h of parathyroid hormone treatment; these activities returned to control values after 48 h and were increased substantially (twice control levels) after 96 h of treatment with the hormone. Subcellular fractionation studies to identify the route of uptake and degradation of collagenase-3 localized intracellular accumulation of 125I-rat collagenase-3 initially in Golgi-associated lysosomes and later in secondary lysosomes. Maximal lysosomal accumulation of the radiolabel and stimulation of general lysosomal activity occurred after 72 h of parathyroid hormone treatment. Preventing fusion of endosomes with lysosomes (by temperature shift, colchicine, or monensin) resulted in no internalized 125I-collagenase-3 in either lysosomal fraction. Treatment of UMR cells with the above agents or ammonium chloride decreased excretion of 125I-labeled degradation products of collagenase-3. These experiments demonstrated that degradation of collagenase-3 required receptor-mediated endocytosis and sequential processing by endosomes and lysosomes. Thus, parathyroid hormone regulates the expression and synthesis of collagenase-3 as well as the abundance and functioning of the collagenase-3 receptor and the intracellular degradation of its ligand. The coordinate changes in the secretion of collagenase-3 and expression of the receptor determine the net abundance of the enzyme in the extracellular space.

Alkaline Phosphatase↗
PubMed1998

Non-English speaking background high school students' attitudes towards the nursing profession.

Australia is a multicultural nation with its population coming from over 120 different cultural backgrounds. With the arrival of new immigrants from Southeast Asia, China, Korea and Lebanon over the last 20 years, issues such as the recruitment of bilingual and cross-cultural knowledgeable nurses have become a high priority within the health care system. However, recruiting these skilled professionals has been difficult. This study aimed to examine (1) non-English speaking background (NESB) high school students' career preferences in relation to nursing; and (2) whether nursing is perceived differently by the Korean, Lebanese, Vietnamese and mainland Chinese high school students. A convenience sample of 162 NESB high school students with parents from Korea, Lebanon, Vietnam and China was recruited from Sydney, New South Wales, Australia. Data were collected by a questionnaire to measure students' knowledge about, attitudes towards and intention to study nursing and their demographic details. Descriptive and inferential statistics were used to describe students' demographic background, their career preference and to compare knowledge, attitudes and intention scales among the NESB groups. Results indicated that less than 10% of students included nursing among their preferred career options. Korean students scored lower than the other NESB groups on attitude and intention towards nursing. The findings provide clues as to how nursing can be better promoted to NESB school leavers. Limitations of the study were discussed and recommendations were suggested for future research.

Adolescent↗
PubMed1998

The temporal profile and morphologic features of neuronal death in human stroke resemble those observed in experimental forebrain ischemia: the potential role of apoptosis.

Although neuronal death has been studied in experimental models of ischemia, the precise mechanisms regulating cell death remain unclear. Furthermore, the timing and pattern of neuronal death in human stroke has not been extensively studied. To further our understanding of ischemia-induced neuronal death, we examined the temporal profile of histochemical and morphologic characteristics of hippocampal neuronal death following experimental forebrain ischemia and compared these findings to human brain specimens obtained from subjects suffering cerebral infarction. Transient forebrain ischemia (TFI) was induced in normothermic adult rats by bilateral carotid artery occlusion combined with hypotension. Animals were sacrificed at 6, 12, 18, 24, 48, and 72 h and 7, 14, and 28 days following ischemia (n = 4 at each time point). Experimental tissue was analyzed using light and electron microscopy as well as TUNEL histochemistry. A total of 27 human brain specimens with neuropathological confirmation of ischemic damage and appropriate controls were also examined using light microscopy and TUNEL histochemistry. Dense TUNEL staining in hippocampal CA-1 neurons was present at 48 and 72 h following experimental ischemia. Prior to these times, little or no nuclear staining was noted and after 72 h nuclear staining diminished rapidly. Ultrastructural findings at these time points demonstrated many features similar to those seen in cells undergoing apoptosis, such as cell shrinkage with increased electron density, chromatin condensation with formation of heterochromatin, intact plasma membranes, and intact intracellular organelles. In a similar fashion, human stroke specimens during the subacute period showed dense nuclear TUNEL staining in penumbral neurons, whereas in the acute or chronic stages little or no staining was noted. Our results demonstrate that the timing of morphologic changes and TUNEL histochemistry following human stroke resembles that observed in experimental TFI. Furthermore, neuronal death in both experimental ischemia and human stroke share several features characteristic of apoptotic cell death.

Adolescent↗
PubMed1998

Primary non-Hodgkin's lymphoma of the nose and nasopharynx: clinical features, tumor immunophenotype, and treatment outcome in 113 patients.

PURPOSE: To study the clinical features and outcome for primary non-Hodgkin's lymphomas of the nose/nasopharynx (NNP-NHLs) according to immunophenotype. PATIENTS AND METHODS: One hundred thirteen Chinese patients with primary NNP-NHLs that belonged to the categories E, F, G, or H according to the Working Formulation (WF), with full immunophenotypic data and complete clinical follow-up data, were analyzed in this retrospective study. RESULTS: Ninety (79.6%) patients had localized (stage I or II) disease, while 23 (20.4%) had stage III or IV disease. The lymphomas in 51 (45.1%), 24 (21.3%), and 38 (33.6%) patients showed natural killer (NK)/T- (CD56-positive), T-cell, and B-cell immunophenotype, respectively. Seventy-three patients (65.8%) achieved a complete remission, of whom 34 (46.6%) subsequently relapsed. The median follow-up time for those alive was 88 months. The 5-year actuarial disease-free and overall survival rates were 34.4% and 37.9%, respectively. Multivariate analysis showed that only stage and immunophenotype were significant for survival. NK/T lymphomas were distinctive among the three immunophenotypes in the following aspects: the highest male-to-female ratio, more frequent involvement of the nasal cavity alone, higher risk of dissemination to the skin, more frequent development of hemophagocytic syndrome, and the worst prognosis (overall median survival, 12.5 months). CONCLUSION: The three immunophenotypes studied are shown to exhibit different clinical patterns. Since the NK/T phenotype carries the worst prognosis, patients who present with NNP-NHL should have their tumors analyzed for CD56 expression.

Adolescent↗
PubMed1997

Polycythemia vera in Chinese patients: thirty-six years of experience.

Forty-one patients with polycythemia vera (PV) according to the PVSG criteria were analysed retrospectively from January 1960 to March 1996. There were 23 male and 18 female patients with a median follow-up of 66.5 months (3-431 months). Median age was 62 (range: 37-85). The median hemoglobin level at diagnosis was 18.8 g/dl. Four patients were treated by venesection alone, 20 patients received hydroxyurea and intermittent venesection, 3 were treated with radioactive phosphorus alone, and 14 had both hydroxyurea and radioactive phosphorus. During the course of illness, 14 patients (34%) developed a total of 19 thrombotic events. Of the thrombotic events, 16 were arterial and 3 were venous. Two patients had both arterial and venous thrombosis sequentially. The probability of thrombosis-free survival after treatment was 83% at 10 years and 73% at 20 years. One patient developed post-polycythemic myeloid metaplasia 24 months after diagnosis. Of 17 patients exposed to radioactive phosphorus, only 1 developed secondary acute myeloid leukemia (AML) 9 years afterwards. Of the 20 patients treated with hydroxyurea for a median duration of 63.5 months (2-130 months), there is no case of secondary malignancy. Overall survival was 83% at 10 years and 62% at 20 years. In conclusion, PV in Chinese is a relatively benign disease with a low risk of thrombosis as compared to Caucasian patients. Hydroxyurea has a very low risk of secondary leukemia and is a safe drug to use in Chinese patients with PV.

Adult↗
PubMed1996

Antioxidant activity of natural flavonoids is governed by number and location of their aromatic hydroxyl groups.

We studied antioxidant activity of five natural flavonoids in canola oil, an emulsion, and rat red blood cell membrane. In the canola oil heated at 105 degrees C, myricetin most effectively attenuated lipid oxidation, followed by quercetin, morin and kaempferol in a decreasing order. When the emulsion containing canola oil was incubated at 54 degrees C, quercetin was most protective against lipid oxidation, followed by kaempferol, myricetin and morin in a decreasing rank. Apigenin demonstrated no antioxidant activity in either the canola oil or the emulsion. Of the flavonoids tested, quercetin was the best in quenching free radical chain reaction in rat red blood cell membrane. The antioxidative characteristics of these flavonoids was determined by multiple factors including the system used, the hydrophobicity, and the total number and the location of aromatic hydroxyl groups. We conclude that myricetin is an effective antioxidant in canola oil, while quercetin is an effective protector against lipid oxidation in the cell membrane.

Animals↗
PubMed1996

7-Nitroindazole: a selective inhibitor of penile erection: an in vivo study in a rat animal model.

OBJECTIVES: The neuronal isoform of nitric oxide synthase (nNOS) has been localized in neurons innervating the penis and is believed to be an important mediator of erection. Using the selective inhibitor 7-nitroindazole (7-NI), we evaluated the possible role of nNOS in penile erection using a rat animal model. METHODS: Eighteen Sprague-Dawley rats were divided into three study groups. A sham group (n = 6) received the vehicle arachis oil, a low-dose group received 5 mg/kg (n = 6), and a high-dose group received 50 mg/kg (n = 6) of 7-NI prior to measurement of blood pressure and cavernous nerve stimulation-induced rise in intracavernous pressure. RESULTS: A dose-dependent inhibition of erection by 7-NI was seen. Control animals had an intracavernous pressure rise of 55.5 +/- 4.0 cm H2O, whereas the low-dose group had 26.5 +/- 2.8 cm H2O and the high-dose group had 6.2 +/- 2.1 cm H2O. A partial recovery of erection was seen in the low- and high-dose groups after 3 hours. Blood pressure was unaffected by 7-NI administration. CONCLUSIONS: 7-NI induced a reversible, dose-dependent inhibition of erection without affecting blood pressure. This in vivo study provides further evidence of the role played by nNOS in erection.

Analysis of Variance↗
PubMed1996

The regulation and regulatory role of collagenase in bone.

Interstitial collagenase plays an important role in both the normal and pathological remodeling of collagenous extracellular matrices, including skeletal tissues. The enzyme is a member of the family of matrix metalloproteinases. Only one rodent interstitial collagenase has been found but there are two human enzymes, human collagenase-1 and -3, the latter being the homologue of the rat enzyme. In developing rat and mouse bone, collagenase is expressed by hypertrophic chondrocytes, osteoblasts, and osteocytes, a situation that is replicated in a fracture callus. Cultured osteoblasts derived from neonatal rat calvariae show greater amounts of collagenase transcripts late in differentiation. These levels can be regulated by parathyroid hormone (PTH), retinoic acid, and insulin-like growth factors, as well as the degree of matrix mineralization. Much of the work on collagenase in bone has been derived from studies on the rat osteosarcoma cell line, UMR 106-01. All bone-resorbing agents stimulate these cells to produce collagenase mRNA and protein, with PTH being the most potent stimulator. Determination of secreted levels of collagenase has been difficult because UMR cells, normal rat osteoblasts, and rat fibroblasts possess a scavenger receptor that removes the enzyme from the extracellular space, internalizes and degrades it, thus imposing another level of control. PTH can also regulate the abundance of the receptor as well as the expression and synthesis of the enzyme. Regulation of the collagenase gene by PTH appears to involve the cAMP pathway as well as a primary response gene, possibly Fos, which then contributes to induction of the collagenase gene. The rat collagenase gene contains an activator protein-1 sequence that is necessary for basal expression, but other promoter regions may also participate in PTH regulation. Thus, there are many levels of regulation of collagenase in bone perhaps constraining what would otherwise be a rampant enzyme.

Animals↗