PubMed Health⌕ Search

Biomedical subjects

H L Chan

Publications and source records attributed to H L Chan.

At least 19 recordsLinked to original sources

Preventing recurrent upper gastrointestinal bleeding in patients with Helicobacter pylori infection who are taking low-dose aspirin or naproxen.

BACKGROUND: Many patients who have had upper gastrointestinal bleeding continue to take low-dose aspirin for cardiovascular prophylaxis or other non-steroidal antiinflammatory drugs (NSAIDs) for musculoskeletal pain. It is uncertain whether infection with Helicobacter pylori is a risk factor for bleeding in such patients. METHODS: We studied patients with a history of upper gastrointestinal bleeding who were infected with H. pylori and who were taking low-dose aspirin or other NSAIDs. We evaluated whether eradication of the infection or omeprazole treatment was more effective in preventing recurrent bleeding. We recruited patients who presented with upper gastrointestinal bleeding that was confirmed by endoscopy. Their ulcers were healed by daily treatment with 20 mg of omeprazole for eight weeks or longer. Then, those who had been taking aspirin were given 80 mg of aspirin daily, and those who had been taking other NSAIDs were given 500 mg of naproxen twice daily for six months. The patients in each group were then randomly assigned separately to receive 20 mg of omeprazole daily for six months or one week of eradication therapy, consisting of 120 mg of bismuth subcitrate, 500 mg of tetracycline, and 400 mg of metronidazole, all given four times daily, followed by placebo for six months. RESULTS: We enrolled 400 patients (250 of whom were taking aspirin and 150 of whom were taking other NSAIDs). Among those taking aspirin, the probability of recurrent bleeding during the six-month period was 1.9 percent for patients who received eradication therapy and 0.9 percent for patients who received omeprazole (absolute difference, 1.0 percent; 95 percent confidence interval for the difference, -1.9 to 3.9 percent). Among users of other NSAIDs, the probability of recurrent bleeding was 18.8 percent for patients receiving eradication therapy and 4.4 percent for those treated with omeprazole (absolute difference, 14.4 percent; 95 percent confidence interval for the difference, 4.4 to 24.4 percent; P=0.005). CONCLUSIONS: Among patients with H. pylori infection and a history of upper gastrointestinal bleeding who are taking low-dose aspirin, the eradication of H. pylori is equivalent to treatment with omeprazole in preventing recurrent bleeding. Omeprazole is superior to the eradication of H. pylori in preventing recurrent bleeding in patients who are taking other NSAIDs.

Anti-Bacterial Agents↗

Lamivudine treatment for fulminant hepatic failure due to acute exacerbation of chronic hepatitis B infection.

BACKGROUND: Exacerbation of chronic hepatitis B infection can lead to fulminant hepatic failure with a mortality of up to 90%. AIM: To evaluate the efficacy of lamivudine in the treatment of this subgroup of patients. METHODS: Twenty-four patients with exacerbation of chronic hepatitis B infection and fulminant hepatic failure were treated with lamivudine, 100 mg daily. Hepatitis A, C, D and human immunodeficiency virus co-infections and hepatocellular carcinoma were excluded. RESULTS: The median age was 53 years (range, 24-77 years) with a male predominance of 20:4. Seventeen patients were hepatitis B e antigen positive. Mean hepatitis B virus DNA was 2079 Meq/mL. Eight patients (33%) survived (group A). Thirteen patients died and three patients received liver transplantation (67%) (group B). Baseline laboratory results were comparable between the two groups, including serum albumin, bilirubin, alanine aminotransferase, prothrombin time and creatinine. Group B patients had significantly more comorbid illnesses at baseline and more complications, including sepsis and renal failure, compared with group A patients. Six out of eight survivors (75%) had full hepatitis B e antigen seroconversion, but this was not sustained in four patients. CONCLUSIONS: Lamivudine may be useful in treating patients with fulminant hepatic failure due to exacerbation of chronic hepatitis B. Hepatitis B e antigen seroconversion was less durable in this subgroup of patients and long-term therapy may be required.

Administration, Oral↗

The efficacy of thymosin in the treatment of chronic hepatitis B virus infection: a meta-analysis.

BACKGROUND: Trials of thymosin treatment in chronic hepatitis B virus infection have been small and the results have been inconsistent. AIM: To conduct a meta-analysis to evaluate the efficacy of thymosin treatment in chronic hepatitis B virus infection. METHODS: Randomized controlled trials comparing thymosin for over 24 weeks vs. placebo (or usual care) in the treatment of chronic hepatitis B virus infection were identified through MEDLINE, EMBASE and the Cochrane Register of Clinical Trials. Biochemical (normalization of transaminases) and virological (loss of hepatitis B virus DNA and hepatitis B e antigen) responses were analysed using the intention-to-treat method. The odds ratio was used to measure the magnitude of the efficacy. RESULTS: Five trials (353 patients) were identified. The odds ratio (95% confidence interval) of the virological response of thymosin over placebo at the end of treatment, 6 months post-treatment and 12 months post-treatment were 0.56 (0.2-1.52), 1.67 (0.83-3.37) and 2.67 (1.25-5.68), respectively. There was an increasing trend of the virological response with time since the cessation of thymosin treatment (P=0.02). There was no difference in the biochemical response between the thymosin and placebo groups at the end of treatment, 6 months post-treatment and 12 months post-treatment. CONCLUSIONS: Thymosin is effective in suppressing viral replication in chronic hepatitis B virus infection, but the effect is delayed until 12 months after the cessation of treatment.

Antiviral Agents↗

Granulomatous variant of chronic pigmented purpuric dermatosis: report of two cases.

Two patients presenting with chronic pigmented purpuric dermatosis (CPPD) on the dorsum of both feet were found to show granulomatous inflammation superimposed on the pathological changes of CPPD. Two similar cases have been reported from Japan. The unique clinicopathological features of this group of patients suggest that they have a rare granulomatous variant of CPPD.

Aged↗

Is non-Helicobacter pylori, non-NSAID peptic ulcer a common cause of upper GI bleeding? A prospective study of 977 patients.

BACKGROUND: Non-Helicobacter pylori, non-NSAID ulcer is relatively common in Western countries. Whether it is a significant problem in the Orient is unclear. The aim of this study was to investigate the incidence of non-H pylori, non-NSAID ulcers presenting with GI bleeding. METHODS: A prospective study was done of 1675 consecutive patients presenting with upper GI bleeding over a period of 12 months. Upper endoscopy was performed with biopsy specimens taken from the antrum and body of the stomach for a biopsy urease test (BUT) and histology for detection of H pylori. Exposure to nonsteroidal anti-inflammatory drugs (NSAID) or aspirin within 4 weeks of hospitalization was carefully scrutinized. A 6-week course of treatment with an H2-receptor antagonist was prescribed for patients who did not use an NSAID and had a negative BUT result. Follow-up endoscopy was performed to confirm H pylori status with a BUT and histology. Positive histology at either initial or follow-up endoscopy was used as the standard for diagnosing H pylori infection. RESULTS: Among 977 patients who were found to have ulcer bleeding, 434 (44%) had exposure to aspirin or an NSAID. Of the 543 non-NSAID users, 431 (79.4%) had a positive BUT and 112 (20.6%) were BUT negative on initial endoscopy. Eighty-nine of 112 patients who were NSAID negative, BUT negative returned for follow-up endoscopy. Forty-nine of 89 (55.1%) were found to have a positive BUT and positive histology at follow-up endoscopy. Only 40 of 977 (4.1%) patients admitted with ulcer bleeding were confirmed to have non-H pylori, non-NSAID ulcers. CONCLUSIONS: Non-H pylori, non-NSAID bleeding ulcer is uncommon. A negative BUT is unreliable for exclusion of H pylori infection during the acute phase of ulcer bleeding.

Adolescent↗

PCLT/P (VDF-TrFE) nanocomposite pyroelectric sensors.

Thin composite films consisting of 12 vol% of nanosized lanthanum and calcium-modified lead titanate (PCLT) powder embedded in a vinylidene fluoride-trifluoroethylene copolymer [P(VDF-TrFE)] matrix were deposited on silicon (Si) substrates to form pyroelectric sensors with three different configurations. The influences of a thermal buffer layer and back etching of the silicon substrate on the current and voltage responsivities of the sensors were investigated theoretically and experimentally. The specific detectivity of the sensors was also calculated from the measured voltage responsivity and noise.

Journal Article↗

A standing wave-type noncontact linear ultrasonic motor.

In this study, a novel standing wave-type noncontact linear ultrasonic motor is proposed and analyzed. This linear ultrasonic motor uses a properly controlled ultrasonic standing wave to levitate and drive a slider. A prototype of the motor was constructed by using a wedge-shaped aluminum stator, which was placed horizontally and driven by a multilayer PZT vibrator. The levitation and motion of the slider were observed. Assuming that the driving force was generated by the turbulent acoustic streaming in the boundary air layer next to the bottom surface of the slider, a theoretical model was developed. The calculated characteristics of this motor were found to agree quite well with the experimental results. Based on the experimental and theoretical results, guidelines for increasing the displacement and speed of the slider were obtained. It was found that increasing the stator vibration displacement, or decreasing the gradient of the stator vibration velocity and the weight per unit area of the slider, led to an increase of the slider displacement. It was also found that increasing the amplitude and gradient of the stator vibration velocity, or decreasing the weight per unit area of the slider and the driving frequency, gave rise to an increase of the slider speed. There exists an optimum roughness of the bottom surface of the slider at which the slider speed has a maximum.

Journal Article↗

Time-Frequency analysis of heart rate variability during transient segments.

The spectral characteristics of heart rate variability (HRV) are related to the modulation of the autonomic nervous system. As the physiological condition is changed by such external stimuli such as drugs, postural changes, and anesthesia, or by internal deregulation such as in syncope, adjective autonomic responses could alter HRV characteristics. Time-frequency analysis is commonly used to investigate the time-related HRV characteristics. An alteration of the autonomic regulation resulting in a change in mean heart rate induces a transient component in heart rate, which, with any analysis method based on signals from multiple beats, results in the apparent spread of the spectrum of frequencies. This obscures the spectral components related to the autonomic function. In this paper we investigated the influence of the transient component in several time-frequency methods including the short-time Fourier transform, the Choi-Williams distribution, the smoothed pseudo Wigner-Ville distribution (SPWVD), the filtering SPWVD compensation, and the discrete wavelet transform. One simulated signal and two heart rate signals during general anesthesia and postural change were used for this assessment. The result demonstrates that the filtering SPWVD compensation and the discrete wavelet transform have small spectrum interference from the transient component.

Anesthesia, General↗

Lack of intravenous lidocaine effects on HRV changes of tracheal intubation during induction of general anesthesia.

BACKGROUND: Intravenous lidocaine has been widely used for suppressing the autonomic activation from tracheal intubation during induction of general anesthesia. Conventionally, researches of its effectiveness through assessment of heart rate and blood pressure changes obtained by common clinical methods result in the conclusions deduced of much controversy. Heart rate variability is a noninvasive measurement of autonomic regulation and is suitable for the study of this subject. METHODS: 36 ASA class I-II patients undergoing general anesthesia were divided into 3 groups. Besides induction agents, intravenous lidocaine was given 5 min before tracheal intubation in group A, 3 min before intubation in group B and nothing in group C. HRV spectral powers were measured at awake state, anesthetized state before tracheal intubation and anesthetized state after tracheal intubation by time frequency spectral analysis method and comparison was made between the three groups. RESULTS: The HRV spectral power in high frequency (HF) and mid-frequency (MF) power bands and their ratios (MF/HF) were not significantly different among the 3 groups during the 3 observation periods. CONCLUSIONS: There was no evidence to indicate the effectiveness of intravenous lidocaine on the autonomic regulation during tracheal intubation under the influence of induction agents used in general anesthesia.

Anesthesia, General↗

Sézary syndrome in a Malay--case report and literature review.

Sézary syndrome is a rare form of primary cutaneous T cell lymphoma. It is a distinct systemic variant of mycosis fungoides, marked by erythroderma, lymphadenopathy and circulating cerebriform lymphocytes in the peripheral blood. We report a case of Sézary syndrome in a 61-year-old Malay man with a five-year history of indurated plaques, ulcers and tumours on the head and trunk, with characteristic findings on physical examination, skin biopsy, electron microscopy, immunophenotyping and peripheral blood film. A literature review on Sézary syndrome is presented.

Biopsy↗

Association of pityriasis rosea with human herpesvirus-6 and human herpesvirus-7 in Taipei.

BACKGROUND AND PURPOSE: Pityriasis rosea (PR) is a common papulosquamous skin disease with unknown etiology. The possible relationship of PR with human herpesvirus infection (HHV) has been extensively studied. This study used the polymerase chain reaction (PCR) to investigate the presence of human herpesvirus 6 and 7 (HHV-6 and HHV-7) in 41 PR patients from two hospitals in Northern Taiwan. The epidemiologic features of PR in patients were also studied. METHODS: A total of 41 PR patients (11 males, 30 females) were enrolled in this study from April 1999 to March 2000. PCR of skin biopsy specimens from 24 PR patients was used to identify the existence of HHV-6 and HHV-7. Viral culture from PR biopsy specimens was also performed. Blood from these patients was sampled for Venereal Disease Research Laboratory tests. Skin biopsies from 20 age- and sex-matched controls with other skin diseases were also subjected to PCR study. RESULTS: The ages of the 41 PR patients ranged from 8 to 62 years. An increased incidence (17/41) of PR episodes was observed during the spring. Both HHV-6 and HHV-7 DNA was below the limit of detection in all biopsy specimens from patients and healthy controls. Viral culture for HHV was negative in all patients. CONCLUSION: The epidemiologic features of PR in this series are comparable to other studies except for an exaggerated female predominance (male:female ratio 1:2.7). Our data indicate a lack of association between HHV-6 and HHV-7 infection and PR.

Adolescent↗

Hepatitis B virus reactivation during cytotoxic chemotherapy-enhanced viral replication precedes overt hepatitis.

The diagnosis of HBV reactivation during cytotoxic chemotherapy is based on an abrupt rise in levels of serum HBV DNA in conjunction with a hepatitic picture and in the absence of other causes of hepatitis. However, several cases of "hepatitis" have been noted during chemotherapy in HBsAg-positive patients, for which no cause could be found and in which HBV DNA levels were negative. One possible explanation is that HBV reactivation may, indeed, have been the cause but that HBV DNA levels became negative by the time ALT levels peaked and the clinical diagnosis of hepatitis was made. During the course of a longitudinal study of HBsAg-seropositive cancer patients who were monitored during standard chemotherapy, the opportunity was available to test this hypothesis.

Adult↗

Hepatitis B e antigen-negative chronic hepatitis B in Hong Kong.

Hepatitis B e antigen-negative chronic hepatitis B (e-CHB) has been reported in Asia but its prevalence and clinical significance have not been determined. The aims of this study were to determine the prevalence of e-CHB in Hong Kong and the frequency of precore and core promoter mutations in these patients. A cross-sectional study was performed in 350 consecutive Chinese patients (230 men and 120 women; mean age +/-SD, 42 +/- 13 years) with chronic hepatitis B virus infection. A total of 243 (69%) patients were hepatitis B e antigen (HBeAg)-negative of whom 15% had clinical cirrhosis. In the remaining 85% of patients, 63% had normal and 22% had elevated transaminases. Serum hepatitis B virus (HBV) DNA was detectable using branched DNA assay in 46% of HBeAg-negative patients with clinical cirrhosis/elevated transaminases. Forty-five percent of the patients with e-CHB had the precore stop codon mutation, and an additional 41% had core promoter changes. There was no correlation between the presence of precore/core promoter mutations and liver disease or HBV-DNA levels. Overall, 17% of HBeAg-negative patients were viremic and had evidence of chronic liver disease (e-CHB) with mean HBV-DNA levels comparable with that in HBeAg-positive patients. In summary, we found that e-CHB may be present in up to 17% of HBeAg-negative patients seen in a tertiary referral center in Hong Kong. e-CHB may be a heterogeneous condition and is not invariably associated with the precore HBV mutant. Population studies are needed to determine the true prevalence of e-CHB in Asia and to assess its natural course and response to treatment.

Adolescent↗

Dermatofibroma is a clonal proliferative disease.

Benign fibrous histiocytoma of the skin or dermatofibroma (DF) has been regarded as a fibrohistiocytic tumor. Whether DF is a neoplastic growth or a reactive process has not been settled. Since a neoplastic process is clonal in nature, clonal analysis of DF was conducted to see if DF is a clonal disease. Fresh specimens of 13 DFs and 2 hypertrophic scars obtained from female patients were studied. The adjacent nonlesional skin tissues served as controls. The clonal analysis was based on the methylation pattern of the polymorphic X-chromosome linked androgen-receptor gene (HUMARA). Eight DFs and 1 hypertrophic scar were heterozygous at the androgen receptor gene and could be analyzed. All 8 informative DFs showed a significant reduction in one of the allelic bands compared with the corresponding bands of the nonlesional tissue after Hha I digestion. Therefore, DF is a clonal proliferative disease. In contrast, 1 hypertrophic scar showed a polyclonal pattern of X-chromosome inactivation. We conclude that DF is a clonal disease favoring a neoplastic process.

Alleles↗

Toxic epidermal necrolysis following combination of methotrexate and trimethoprim-sulfamethoxazole.

A 15-year-old boy with T-cell acute lymphoblastic leukemia (ALL) (FAB L1), diagnosed in 1995, received combination chemotherapy consisting of 6 weeks of induction (vincristine, epirubicin, L-asparaginase, prednisolone) and 2 weeks of consolidation (cytosine arabinosides, etoposide). After achieving remission, for further maintenance of remission, he was treated with 14 cycles of intensive chemotherapy consisting of 6-MP, 10 mg/kg orally on the first 4 days, and cyclophosphamide, 1200 mg/m2, vincristine, 1.5 mg/m2, epirubicin, 15 mg/m2, and cytosine arabinoside, 40 mg/m2, intravenously on days 4, 11, 39, and 40, respectively. On day 18 of each cycle, he received intravenous methotrexate (MTX) infusion in a total dose of 150 mg/m2 plus oral leucovorin (30 mg/m2 ) rescue 36 h after starting MTX therapy. In addition, oral trimethoprim-sulfamethoxazole was given regularly to prevent Pneumocystis carinii infection. The patient achieved remission during the first course of treatment, but 8 months later the disease relapsed. He then received four doses of MTX (800 mg intravenously) plus leucovorin rescue in the following 4 months. During the last MTX therapy, small hemorrhagic bullae were found on the lateral side of the right ankle, but subsided after a few days. Due to partial remission of the disease, he was admitted again in January 1999 for high-dose MTX therapy. An initial hemogram on admission revealed hemoglobin 7.2 g/dL, white cell count 15,200/mm3, platelet count 153/mm3, blood creatinine 0.5 mg/dL, and alanine leucine aminotransferase (ALT) 20 U/L. He received 8500 mg of MTX (5000 mg/m2 ) as a continuous intravenous infusion for 24 h. Thirty-six hours after the start of MTX infusion, leucovorin (30 mg, intravenous) rescue was initiated every 6 h for 3 days. Another preventive measure to cover MTX toxicity included aggressive intravenous fluid replacement (4 L/m2 /day) and the addition of 25 meq/L sodium bicarbonate to the intravenous fluid to alkalinize the urine. Concurrent medication included 6-MP (50 mg) once daily and trimethoprim-sulfamethoxazole (120 mg, 600 mg) twice daily every other day. Plasma MTX levels were 52.36 micromol/L 24 h after MTX infusion, 1.87 micromol/L after 48 h, 0.57 micromol/L after 72 h, and 0.41 micromol/L after 96 h. These indicated delayed MTX plasma clearance. The blood creatinine level was mildly elevated from 0.5 mg/dL to 0.7 mg/dL. Thirty-six hours after the administration of MTX, the patient developed an erythematous painful swelling on the right middle finger. The erythema, with subsequent large bulla formation, progressed to all the fingers, toes, palms, and the soles of the feet. Some erythematous to hemorrhagic papules also appeared on the bilateral elbows. Subsequently, diffuse tender erythema with extensive erosions and focal tiny pustules developed on the back, abdomen, proximal extremities, and face (Fig. 1a,b). A positive Nikolsky's sign was also present. A biopsy specimen of the right dorsal hand lesion revealed parakeratosis, detached acanthotic epidermis with scattered necrotic keratinocytes, dyskeratotic cells and nuclear atypia, neutrophilic exocytosis, and many neutrophils in the papillary dermis (Fig. 2). The skin condition deteriorated rapidly. Toxic epidermal necrolysis-like lesions involved 90% of the total body surface on the fifth day after MTX infusion. Mucositis, diarrhea, involuntary tremor, fever, and chills were noted. The patient was then sent to the burn unit for intensive skin care. Ten days after MTX therapy, profound agranulocytosis and thrombocytopenia (white cell count 100/mm3, platelets 14,000/mm3, and hemoglobin 5.6 g/dL) were found. The patient was then started on granulocyte colony stimulation factor (G-CSF, 5 microg/kg/day), but his general condition deteriorated rapidly and he died 6 days later due to septic shock and multiple organ failure.

Adolescent↗

Decreased autonomic nervous system activity as assessed by heart rate variability in patients with chronic tetraplegia.

OBJECTIVES: To assess the alterations of autonomic nervous functions and sympathovagal balance of the subjects with spinal cord injuries (SCIs) in different levels by heart rate variability analysis. DESIGN: Prospective, observational study. SETTING: All participants were recruited from the outpatient clinic from National Taiwan University Hospital, which is a tertiary referral center. PARTICIPANTS: Thirty-one patients with traumatic chronic complete SCI (more than 6 months): 14 with paraplegia (Group A), and 17 with tetraplegia (Group B). MAIN OUTCOME MEASURES: Heart rate variability assessed by 24-hour Holter monitoring. RESULTS: Two patients in Group A and 1 in Group B were excluded from final data analysis because of poor recording data. Two time domain variables, the standard deviation (SD) of all normal RR intervals (SDNN) and the mean of the SDs of all normal RR intervals for all 5-minute intervals (SDNNi), over 24 hours were decreased in Group B. All time domain variables, SDNN, SDNNi, root mean square of the successive normal RR interval difference (rMSSD), and the percentage of RR intervals differing >50msec from the preceding one (pNN50), were decreased during the nighttime recordings (all p < .05) in Group B. The very-low-frequency, low-frequency (LF), and high-frequency (HF) components of the power spectrum of the RR intervals were also decreased in Group B (p < .05), irrespective of the daytime and nighttime recordings. The LF-to-HF ratio did not differ significantly in these two groups, indicating the maintained sympathovagal balance in the chronic SCI patients. CONCLUSION: These findings suggested that the autonomic nervous system activity was depressed in the patients with chronic tetraplegia, but the autonomic nervous system still maintained homeostasis.

Adult↗

Toxicity and DNA binding of dextran-doxorubicin conjugates in multidrug-resistant KB-V1 cells: optimization of dextran size.

We previously showed that conjugating doxorubicin to very large 70-500 kDa dextran decreased its removal rate from P-glycoprotein (P-gp) over-expressing, multidrug-resistant KB-V1 cells. Furthermore these conjugates could act synergistically with other cancer drugs. In the drug-sensitive 3-1 clone, but not in the V1 subclone which was 300-fold more resistant to free doxorubicin, conjugation led to a size-related decrease in toxicity. Here we identified the optimal size of dextran for avoiding P-gp-mediated efflux and yet preserving as much as possible doxorubicin toxicity. Chemically reduced, intracellularly stable 3.4-10 kDa conjugates were prepared. Confocal microscopy and fluorescence quenching experiments showed that these conjugates entered nuclei and interacted with DNA. In 3-1 cells, but not in V1 cells, cytotoxicity of conjugates decreased 14- to 45-fold linearly related to log size of the carrier (r=0.95). In V1 cells toxicity of the 10 kDa conjugate exceeded that of free doxorubicin. After conjugation the equilibrium binding constant of the DNA-drug complex (KA) decreased only by up to 3-fold. In 3-1 cells, but not in VI cells, DNA binding kinetics was an important factor and toxicity could be linearly correlated to 1/KA of conjugate (r=0.94). Drug accumulation decreased with an increase in dextran size but drug removal was decreased only in V1 cells. It appeared that drug uptake was also sensitive to dextran conjugation. In Vl cells drug removal was sensitive to the P-gp inhibitor verapamil or energy starvation. Ratios of V1/3-1 toxicity, drug accumulation and drug removal correlated linearly with log dextran size. When these ratios equaled 1, dextran sizes were estimated to be 32, 103 and 21 kDa, respectively.

ATP Binding Cassette Transporter, Subfamily B, Mem↗