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Biomedical subjects

H L Chan

Publications and source records attributed to H L Chan.

At least 55 records · Page 3Linked to original sources
PubMed1999

Immunochemical study on beta1-bungarotoxin using polyclonal and monoclonal antibodies.

The number of antigenic determinants of beta1-bungarotoxin (beta1-Bgt), A chain and B chain were determined to be seven, five and two, respectively, by quantitative precipitin reactions and analysis of the soluble complex formed from beta1-Bgt and Fab fragments of the antibody. The gel filtration patterns on a size exclusion column revealed that the soluble complexes formed from non-precipitating antibody and beta1-Bgt at a different molar ratio all emerged in the void volume, indicating that the molecular weight of the soluble complex is around 6000 kDa or more. The gel filtration pattern from Fab fragments of non-precipitating antibody also revealed that only 1 or 2 molecules of Fab fragments are bound to beta1-Bgt, A chain and B chain instead of seven, five and two molecules as in the case of precipitating antibody. Besides, twenty-three stable monoclonal antibodies (mAbs) were prepared against beta1-Bgt by the hybridoma technique. Most of these mAbs cross-reacted with isotoxins of the beta-Bgt family, as determined by an enzyme-linked immunosorbent assay, but none of them reacted with notexin, notechis II-5 and three PLA2 homologues, PLA2, DE-I and CMS-9.

Amino Acid Sequence↗
PubMed1999

Multifocal ERG changes in glaucoma.

The multifocal electroretinogram (MERG) can assess regional retinal responses using analysis which gives both first-order and second-order nonlinear responses from multiple retinal regions. The retinal responses from both types of analysis showed amplitude reduction in glaucoma, suggesting that the outer and inner retinal layers are affected. These findings are in accord with the damage which has been reported in advanced glaucoma. The macular response showed a larger amplitude reduction in b-waves (first-order response) and N2P (second-order response) than did peripheral retinal responses. This indicates that loss of macular response is an important sign in glaucoma.

Adult↗
PubMed1999

Preparation and characterization of beta 1-bungarotoxin bispecific monoclonal antibody.

A hybrid hybridoma (tetradoma) that produces bispecific monoclonal antibodies (mAbs)2, which recognize two different epitopes on the A chain of beta 1-bungarotoxin (beta 1-bgt) at peptide sequences 46-51 and 100-106, has been obtained by fusing two hybridoma cell lines. The bispecific mAb were observed to inhibit 98% of the enzymatic activity of beta 1-bgt and neutralize its lethal toxicity completely. The avidity between the bispecific mAb and beta 1-bgt was noted to be 4.5 x 10(10) (liter/nmol), which is about 45-150 folds higher than the avidity of its two parental mAbs. All the soluble complexes, obtained from bispecific mAb and beta 1-bgt with different molar ratios, emerged in the void volume of size exclusion chromatography column, indicating multiple complexes of beta 1-bgt and bispecific mAb were formed. Based on these results, it indicated that the binding of bispecific mAb with its two epitopes on beta 1-bgt, which facilitates the immuno-complex formation and enhances the avidity, also highly neutralizes the biological activity of beta 1-bgt.

Antibodies, Bispecific↗
PubMed1998

Cytotoxicity and DNA binding characteristics of dextran-conjugated doxorubicins.

The antitumor antibiotic doxorubicin was conjugated with polymeric dextrans of various molecular weights and the cytotoxicity of the conjugates against human carcinoma KB-3-1 cells and its multidrug-resistant subclone KB-V-1 cells was measured by tetrazolium salt MTT assay. The conjugates were much less toxic to the KB-3-1 cells than the free doxorubicin but exhibited similar toxicity to the KB-V-1 cells. The conjugate-DNA interactions were monitored in real-time using an optical biosensor based on evanescent wave detection to obtain the association (ka) and dissociation (kd) rate constants as well as the equilibrium binding constants (KA) of the bindings. Both ka and kd values for the conjugates are more than three magnitudes smaller than those for free doxorubicin, while the KA values of the conjugate-DNA complexes are only about 10 times smaller than that of the free doxorubicin-DNA complex. The results indicate that the cytotoxicity and the DNA-binding kinetics of doxorubicin may be modified with dextran conjugation. The KA values obtained from the biosensor measurements were in close agreement with those determined in solution by fluorescent titration method, verifying the utility of the label-free biosensing measurements as an efficient method for studying ligand-DNA interactions.

Binding Sites↗
PubMed1998

Neutralizing epitope mapping of six beta1-bungarotoxin monoclonal antibodies and its application in beta1-bungarotoxin peptide vaccine design.

Twenty three stable monoclonal antibodies (mAbs) against beta1-bungarotoxin (beta1-bgt) were prepared by the hybridoma technique. Seven of the 23 mAbs (mAbs 2, 6, 8, 11, 17, 21 and 22) could inhibit more than 70% of phospholipase A2 activity of beta1-bgt and neutralize the toxin. Six of these neutralizing mAbs (mAbs 2, 6, 8, 17, 21 and 22) recognized continuous epitopes on the A chain of beta1-bgt and the other one (mAb 11) recognized a conformational epitope on the toxin. The continuous epitopes of these six mAbs were mapped using synthetic peptide and proteolytic enzymes. Experimental results indicate that mAb 17 recognized the A-chain residues 31-37; mAbs 2 and 8 recognized residues 46-51; mAbs 21 and 22 recognized residues 91-98; and mAb 6 recognized residue 100-106. The competitive-antibody-binding inhibition experiments showed that the affinity of these neutralizing mAbs to the native beta1-bgt is compatible with synthetic peptides. Furthermore, mice immunized with BSA-conjugated A-chain-peptide sequences A(31-37), A(46-51), A(91-98) or A(100-106) were protected from a high-dose beta1-bgt challenge. Subsequently, the peptide-immunized sera were passively injected into Balb/c mice and a significantly protective effect was also observed. To our knowledge, this study is the first systematic demonstration of multiple neutralizing B-cell epitopes of beta1-bgt, and this study is also the first report of the protective synthetic-peptide vaccine against beta1-bgt challenge.

Amino Acid Sequence↗
PubMed1998

Does eradication of Helicobacter pylori impair healing of nonsteroidal anti-inflammatory drug associated bleeding peptic ulcers? A prospective randomized study.

BACKGROUND: Despite the widely accepted view that Helicobacter pylori is the most important cause of peptic ulcer disease, recent studies have suggested that the microbe protects against nonsteroidal anti-inflammatory drug (NSAID)-associated gastroduodenal lesions and promotes ulcer healing. We investigated the effects of H. pylori eradication on the healing of NSAID-associated bleeding peptic ulcers. METHODS: Chronic NSAID users presenting with peptic ulcer haemorrhage underwent endoscopy to secure haemostasis and to document H. pylori infection by rapid urease test and culture. They were prospectively randomized to receive either omeprazole (20 mg once daily) for 8 weeks or a 1-week course of triple therapy (bismuth subcitrate 120 mg, tetracycline 500 mg, metronidazole 400 mg, all given four times daily) plus omeprazole (20 mg once daily) for 8 weeks. Endoscopy was repeated after 8 weeks. Final H. pylori status was determined by a 13C-urea breath test that was performed at least 4 weeks after discontinuation of omeprazole. RESULTS: 195 H. pylori-infected NSAID users, complicated by bleeding ulcers, were randomized to receive omeprazole alone (102) or triple therapy plus omeprazole (93). 174 patients returned for second endoscopy at 8 weeks (91 in the omeprazole group, 83 in the triple therapy group). Urea breath test was negative in 14% in the omeprazole group vs. 92% in the triple therapy group (P < 0.001). Complete ulcer healing was achieved in 88 (97%) patients in the omeprazole group and 77 (93%) in the triple therapy group (P=0. 31). On intention-to-treat analysis, ulcers were healed in 86% of the omeprazole group and 83% of the triple therapy group (P=0.50). There was no significant difference in the healing rates of gastric or duodenal ulcers between the two groups. CONCLUSION: Eradication of H. pylori did not impair the healing of NSAID-associated bleeding peptic ulcers.

Adult↗
PubMed1998

Amyopathic dermatomyositis in Hong Kong -- association with nasopharyngeal carcinoma.

BACKGROUND: Amyopathic dermatomyositis (ADM) is a rare variant of dermatomyositis (DM) in which there is no apparent muscle involvement at initial presentation, but clinical and laboratory evidence of myopathy may appear later. Like DM, it has a known association with malignancy. OBJECTIVE: To record the occurrence of ADM in Hong Kong during the period from January 1988 to June 1996, and to establish the types of carcinoma with which it is associated. METHODS: The records of all patients diagnosed with ADM in three major dermatology clinics in Hong Kong were retrospectively studied to confirm the diagnosis and to look for any associated malignancy at any stage of the disease. RESULTS: Between 1988 and 1996, six patients in Hong Kong (five men and one woman; mean age, 50 years) fulfilled the criteria of ADM. During a follow-up period ranging from 20 to 90 months (average, 35.6 months), none developed any evidence of myositis. Associated malignancy was found in the five male patients. There were three cases of nasopharyngeal carcinoma (NPC), one case of non-small cell carcinoma of the lung, and one case of metastatic carcinoma of the cervical lymph node of unknown primary. No carcinoma had developed in the female patient during a follow-up period of 90 months. CONCLUSIONS: There is a strong association between ADM and NPC in Hong Kong.

Adult↗
PubMed1998

Keloidal dermatofibroma: report of 10 cases of a new variant.

Dermatofibroma is a common cutaneous tumor. Unusual variants of dermatofibroma that exhibit various epidermal changes or different cellular composition have been described. We observed 10 cases of a novel variant of dermatofibroma characterized by keloidal change within the tumor. Formalin-fixed, paraffin-embedded tissues were used for histochemical and immunohistochemical studies. The patients consisted of six women and four men; median age was 34 years (17 to 59 years). All tumors occurred on the extremities, and six were present for at least 2 years. Tenderness was mentioned in four cases. They were described as erythematous or brown papules 1 cm or smaller. Clinical appearance did not deviate from that of ordinary dermatofibromas. Microscopically, the excised tumors showed a superficial circumscribed area of keloidal change under an atrophic epidermis in an otherwise ordinary dermatofibroma. In the keloidlike area, multinucleated giant cells, hemorrhage, hemosiderin deposits, and scattered KiM1P-positive histiocytes, but not factor XIIIa-positive or CD34-positive cells were present among the thick collagen fibers. There were no known recurrences. This variant dermatofibroma should not be overlooked as a simple keloidal scar. The observation of keloidal change in dermatofibromas may support the connotation that trauma is a possible cause of dermatofibroma. The fact that Asian people are more prone to develop keloid may have led us to find this new variant.

Adolescent↗
PubMed1998

Evaluation of blood loss during tumescent liposuction in Orientals.

BACKGROUND: There are high risks from general anesthesia and excessive bleeding associated with traditional liposuction using the dry or wet method. The blood loss has been estimated to be between 15% and 45%. The tumescent technique permits liposuction of more than 3,000 ml of fat totally by local anesthesia without sedation. The blood loss is reported to be less than 1% of aspirate. OBJECTIVE: To examine the blood loss during liposuction using tumescent technique in Chinese patients compared with that of Caucasians as published in the literature. METHODS: Hemoglobin values of patient's preoperative venous blood and infranatant of aspirate were measured in 45 consecutive cases of liposuction using the tumescent technique from May 1996 to June 1997. RESULTS: A total of 30 patients completed the study. The average blood loss was estimated to be 1.08% of aspirate. CONCLUSION: From this study, we found the blood loss in Chinese patients is comparable with that in Caucasians. Tumescent liposuction is a safe dermatologic cosmetic surgical procedure without the need of blood transfusion and general anesthesia.

Adult↗
PubMed1998

Experience with laser hair transplantation in Orientals.

BACKGROUND: The advent of high-energy carbon dioxide (CO2) laser-assisted hair transplantation in recent years provides a new recipient area technique for hair restoration surgery. It offers the advantages of less bleeding, time consumption, and graft compression. Specific laser parameters have been recommended in Caucasian but not Oriental patients. OBJECTIVE: To determine the effectiveness as well as appropriate parameters of laser hair transplantation in Oriental patients. METHODS: A Sharplan SilkTouch laser with the Flashscanner set to produce a 0.8-1-mm recipient site hole was employed for all subjects. Various CO2 laser parameters were used to compare the graft survival rate with traditional Nokor needle or microdilator methods for micrografting on each side of the scalp. A total of 20 patients joined the study in the past 18 months. A skin biopsy was performed to examine the tissue effect of the different laser parameters. RESULTS: Hair survival was less than that seen with conventional micrografting techniques in the first five cases, in whom CO2 laser parameters of 36-40 W and 0.2-0.7 seconds were used. After adjusting the parameters to 55 W and 0.1-0.15 seconds, the survival rate increased to between 80% and 90%. In addition, most patients thought the laser-prepared sites resulted in a more natural appearance and better hair density, when they were compared with conventionally prepared sites. CONCLUSIONS: From our study, we find that CO2 laser parameters of 55 W and 0.1-0.15 seconds seem to be the appropriate parameters for Oriental hair transplant patients. Further studies are required to establish laser parameters that will produce better hair survival.

Alopecia↗
PubMed1998

Hibernoma. Case report and literature review.

BACKGROUND: Hibernoma is a rare type of benign tumor that originates in brown fat. It has been rarely described in dermatologic literature. OBJECTIVE: To report and discuss the clinical and histologic features of a patient with hibernoma and review the relevant literature. PATIENT: A large palpable hibernoma located in the interscapular area of a 41-year-old female was identified by physical examination. The tumor was a brown soft mass measuring 7.0 x 6.0 x 3.0 cm that involved subcutaneous tissue and was embedded in the trapzius muscle. It was a well encapsulated and highly vascular tumor. Histologic examination revealed characteristic multivacuolated oval and polygonal cells with eosinophilic, granular cytoplasm. CONCLUSION: A hibernoma can be diagnosed on the basis of gross physical characteristics and microscopic findings. This is a benign tumor with no malignant potential. Excisional biopsy is indicated to differentiate hibernoma from well-differentiated liposarcoma. Complete excision is the treatment of choice.

Adult↗
PubMed1998

The spectrum of cutaneous and internal malignancies in chronic arsenic toxicity.

We report 3 patients of chronic arsenic poisoning with characteristic skin changes. All 3 patients had a past history of asthma and were treated with Traditional Chinese Medication. We believe that the Chinese medications were the source of arsenic poisoning. Two of the 3 patients also had internal malignancy. The association of arsenic with internal malignancy is reviewed.

Arsenic Poisoning↗
PubMed1998

Penicillium marneffei fungemia in an AIDS patient: the first case report in Taiwan.

We report a 36-year-old man with acquired immunodeficiency syndrome (AIDS), presenting systemic Penicillium marneffei (PM) infection. Fungal culture from the blood isolated PM. PM-induced enteritis was also suspected in this patient although there was no direct evidence. He also had other manifestations of immunocompromised status, including military tuberculosis and oral candidiasis. He died of respiratory failure in spite of prompt treatment for infection. This is the first confirmed case of PM infection in Taiwan.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Investigation of retinitis pigmentosa using the multifocal electroretinogram.

Retinitis pigmentosa (RP) patients have pathological changes in both the macula and the periphery, and are known to have abnormal electroretinograms (ERGs). The response densities measured by the multifocal electroretinogram (MERG) in the macula and pericentral retina were greatly reduced in RP. In photopic conditions, some patients had relatively better ERG responses in the macula than in the pericentral retina, and this agreed with the finding that there is usually relatively well-preserved macular function in RP. In scotopic conditions, both macula and pericentral retina gave poor responses. There was very little increase in response as stimulus luminance increased in RP. The topographical mapping of the MERG results can provide objective, localized assessment of retinal function.

Adult↗
PubMed1997

p53 expression and proliferative activity in Bowen's disease with or without chronic arsenic exposure.

A comparative study of Bowen's disease (BD) with or without chronic arsenic exposure may contribute to understanding arsenic carcinogenesis. We compared the p53 overexpression and proliferative activity of 26 cases of BD with chronic arsenic exposure (group I) and 22 comparable cases of BD without chronic arsenic exposure (group II) by immunohistochemical method on formalin-fixed, paraffin-embedded tissues with antibodies PAb1801 and MIB-1, respectively. We also included in this study two squamous cell carcinomas that developed from BD in group I and one in group II. Two paired BD lesions in the same individual of one patient in group I and of three patients in group II were also studied. The significant p53(+) (>10% stained cells) rates were 42.3% (11 of 26) and 9.1% (2 of 22) for groups I and II, respectively, and the difference was statistically significant (P = .01). The p53 expression in different lesions of the same individual remained consistently the same. Squamous cell carcinomas that developed in 2 cases of p53(+) BD in group I were also positive, but the one in 1 case of p53(-) BD in group II was negative. No significant statistical difference in proliferative activity was found between group I BD and group II BD (P= .769), nor between p53(+) cases (>10% stained cells) and p53(-) cases (<10% stained cells) in group I BD (P = .519). This study showed that significant overexpression of p53 protein was higher in BD with chronic arsenic exposure. Therefore, arsenic carcinogenesis of BD might be different from that of BD unrelated to arsenic, and alteration of p53 plays a more important role in the pathogenesis of BD with chronic arsenic exposure. Overexpression of p53 was not a prerequisite for developing squamous cell carcinoma and was not affected by proliferative activity.

Adult↗