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Biomedical subjects

H L Chan

Publications and source records attributed to H L Chan.

At least 109 records · Page 6Linked to original sources
PubMed1991

The effects of topical corticosteroids on human skin.

Topical corticosteroids are widely used on the human skin. The activity of corticosteroids are influenced by their molecular structure. Their action is believed to be mediated through binding to specific glucocorticosteroid receptors in the cytoplasm of cells. The beneficial clinical effects topical corticosteroids are due mainly to its anti-inflammatory property. Percutaneous absorption of topical corticosteroids is affected by variables relating to: (a) the steroid molecular itself, (b) the vehicle in which the ingredient is incorporated and, (c) the skin itself. All these factors must be taken into account in the evaluation of their activity. The more potent the topical corticosteroid, the greater the propensity to cause unwanted effects. Many adverse effects have been reported. Physicians should learn to use these drugs judiciously so as to maximise their desired effects and to minimise their undesired effects.

Administration, Topical↗
PubMed1990

Safety and efficacy of 2% topical minoxidil in the management of male pattern baldness in Chinese.

Topic 2% minoxidil solution has been proved to be effective for hair regrowth in 30-40% of male pattern baldness in the United States and Europe. There was no report concerning topical minoxidil in Chinese patients, therefore, we selected 40 patients to investigate the efficacy and safety from December 1988 to January 1989. Those selected patients were consistent with male pattern baldness without systemic disease, and had never used topical hair regrowth agents. Patients applied topical medication 1 ml twice daily and were examined at 1 month intervals. Thirty two patients completed 6 to 12 months (average 9.6 months) of the study, moderate hair growth was found in 22% while minimal growth in 59% of the studied patients. All patients noted their shedding decrease after the application of drugs for 1 to 3 months. Scalp dryness and mild scaling appeared in 2 patients, but were tolerable. Before and after the trial, all patients had a chest roentgenogram, EKG, complete blood counts, urinalysis and blood chemistry studies, and no apparent abnormality was found. The efficacy of 2% minoxidil solution application in our study was less than that in the United States. which might be because some patients did not follow the application order regularly and a more strict evaluation standard was adopted in our series. However, the safety of no systemic adverse effect and the potential of inhibiting progressive shedding of hair were valuable as a topical drug.

Administration, Topical↗
PubMed1990

Intraepidermal neutrophilic IgA dermatosis.

We report a patient with a vesiculopustular eruption with features distinct from typical subcorneal pustular dermatosis. Clinically, well-formed pustular lesions, which were flowerlike in appearance, were present. Histopathologically, early vesicular lesions showed intraepidermal bullae containing numerous neutrophils, a few eosinophils, and acantholytic cells. Direct immunofluorescence study revealed IgA deposits in the intercellular space of the epidermis. The patient's serum, however, did not contain circulating antibodies reactive with the epidermis. We consider this eruption an immunologically mediated, intraepidermal blistering disease, similar to intraepidermal neutrophilic IgA dermatosis.

Adult↗
PubMed1990

In vitro maturation and encapsidation of the DNA of transposable Mu-like phage D108.

Mu and D108 are related, temperate, transposable coliphages with unusual modes of DNA replication (transposition) and virion DNA maturation. These double-stranded DNA genomes replicate intrachromosomally and are matured and encapsidated linked to DNA sequences flanking the dispersed, integrated phage genomes. We have developed an in vitro system that employs crude lysates prepared from cells late in the Mu lytic cycle and that is proficient for both maturation and encapsidation of D108 DNA. Different forms of phage DNA were packaged at different efficiencies, with a circular pSC101::D108cts10 plasmid being most efficient, linearized plasmid less so, and mature virion DNA a poor substrate. The addition of purified D108 Ner protein to the reaction had no effect, whereas D108 repressor (c protein) inhibited the reaction. Escherichia coli integration host factor and D108 transposase proteins exerted an inhibitory effect on circular DNA substrates but had little effect on linear DNA packaging. This in vitro system, coupled with that developed for transposition, can now be used to biochemically dissect the protein and substrate requirements of these phages' DNA maturation pathway and the nature of the molecular switch between DNA transposition and encapsidation.

Bacteriophage mu↗
PubMed1990

[Nevus sebaceus--a clinicopathological study of 104 cases].

We studied the clinical and histopathologic features of 104 cases of nevus sebaceus observed between January 1983 and December 1988 in the department of Dermatology of Chang Gung Memorial Hospital. There were 48 males and 56 females, the ages ranged from 3 to 60 years, the mean age was 23.5 years old. Among them, most nevus sebaceus developed before age 10 (83%); the most common site of nevus sebaceus was the scalp (70%), followed by the face (26%) and only a few lesions were situated away from the head. Twenty-one cases were associated with secondary tumors in a portion of the lesions were found. In nineteen of the twenty-one patients, the secondary tumors occurred after age 10, their mean age was 30 years old. Of the 25 tumors developed in the 21 patients, 8 were syringocystadenoma papilliferum, 6 were basal cell epithelioma, 4 were trichilemmoma, 3 were sebaceous epithelioma. Multiple tumors were developed in 3 cases of nevus sebaceus. Since a variety of tumors may develop in the nevus sebaceus after puberty, prophylactic removal of nevus sebaceus and close follow-up are suggested.

Adolescent↗
PubMed1990

Cutaneous manifestations of cardiac diseases.

Many general signs familiar to physicians can be found on the skin in cardiac patients. These include (a) cyanosis, central and peripheral, (b) erythremia, flushing and erythema, (c) digital clubbing and (d) alteration in texture. Specific cardiac conditions often have useful diagnostic cutaneous clues. Of these the association of coronary heart disease, hyperlipidemia and xanthomas is the most important. Rare syndromes such as the "leopard syndrome" often have distinctive skin signs. Multisystemic disorders may affect the heart and skin simultaneously or in sequence. They include collagen vascular diseases, amyloidosis, sarcoidosis and relapsing polychondritis. Finally iatrogenic disease arising from treatment of cardiac or cutaneous disease may induce changes in one or the other organ. The heart and the skin have much in common. These manifestations help elucidate the cause, evaluate the diagnosis, and follow the treatment and progress of these diseases.

Heart Diseases↗
PubMed1990

Relapsing polychondritis--a report on two Chinese patients with severe costal chondritis.

Relapsing polychondritis is a rare multisystemic connective tissue disorder found mainly in Caucasians. Oriental patients with relapsing polychondritis are uncommon. We report 2 Chinese patients with relapsing polychondritis who had severe laryngotracheal narrowing requiring tracheostomy. Unlike most patients, there was marked costal chondritis resulting in depression of the anterior chest wall with minimal involvement of other joints. One of the patients had treatment with prednisolone, dapsone, azathioprine, cyclophosphamide and cyclosporin A at various stages of the disease without significant remission of the disease.

Adult↗
PubMed1990

The incidence of erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis. A population-based study with particular reference to reactions caused by drugs among outpatients.

We carried out a study to estimate the incidence of erythema multiforme (EM), Stevens Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) requiring hospitalization and to determine which drug therapies were associated with these reactions. We reviewed the clinical records of all patients who were hospitalized with these discharge diagnoses at Group Health Cooperative (GHC) of Puget Sound, Seattle, Wash, from 1972 through 1986. During this 14-year period, an average of about 260,000 persons, with demographic characteristics similar to those of the general population, received their care from GHC, and there were about 25,000 admissions to hospitals per year at the GHC hospitals. Based on International Classification of Diseases-Adapted coding, a total of 61 suspect cases of EM, SJS, or TEN were identified from the computerized hospital discharge file. Based on record review and the application of a uniform set of diagnostic criteria, a total of 37 patients (61%) were classified as having EM, SJS, or TEN. Of these, 16 cases (43%) were attributed to drugs administered to these patients prior to hospitalization. The overall incidence of hospitalization for EM, SJS, or TEN due to all causes was 4.2 per 10(6) person-years. The incidence of TEN alone due to all causes was 0.5 per 10(6) person-years. The incidence of EM, SJS, or TEN associated with drug use were 7.0, 1.8, and 9.0 per 10(6) person-years, respectively, for persons younger than 20 years of age, 20 to 64 years of age, and 65 years of age and older. Drug therapies with reaction rates in excess of 1 per 100,000 exposed individuals include phenobarbital (20 per 100,000), nitrofurantoin (7 per 100,000), sulfamethoxazole and trimethoprim, and ampicillin (both 3 per 100,000), and amoxicillin (2 per 100,000). Overall, our data suggest that cases of EM, SJS, and TEN sufficiently severe to require hospitalization are infrequent among outpatients using well-established drug therapies. A continuing challenge is the evaluation of these severe cutaneous reactions that are associated with newly marketed or less frequently prescribed drug therapies.

Adolescent↗
PubMed1989

Usefulness of case report literature in determining drugs responsible for toxic epidermal necrolysis.

To evaluate the usefulness of the case report literature concerning toxic epidermal necrolysis, we surveyed English-language reports published from January 1966 to April 1987, using epidermal necrolysis as a key word in the MEDLINE database. Of the 345 articles identified, 80 definitely or possibly contained individual case reports of at least 100 words; 59 of these 82 (72%) were available and reviewed. These 59 reports included a total of 73 separate cases of toxic epidermal necrolysis possibly related to drugs, which represents less than 5% of the case of toxic epidermal necrolysis that occurred in this period. In 62% of these 73 cases the apparent purpose of the report was to show an association between a given drug and the development of toxic epidermal necrolysis. The drugs most frequently associated with toxic epidermal necrolysis are allopurinol, the nonsteroidal anti-inflammatory agents, phenytoin, and the sulfonamide antibiotics. Given that only a small proportion of cases of toxic epidermal necrolysis appear in the case report literature, except to present association with drugs not previously reported, the contribution of case reports in providing an estimate of the relative risk of drug-associated toxic epidermal necrolysis is limited. Furthermore, our analysis suggests that the adoption of specific diagnostic criteria for and more uniform reporting of signs, symptoms, and therapy could greatly increase the usefulness of the case report literature. We propose a minimum set of informational and specific diagnostic criteria.

Adolescent↗
PubMed1989

Use of a fibre-optic hydrophone in measuring acoustic parameters of high power hyperthermia transducers.

A fibre-optic hydrophone consisting of a polarisation-maintaining fibre carrying light from a laser source has been used to measure the acoustic output parameters of a single focused hyperthermia transducer and a six-transducer assembly. Beam profiles of the transducers were measured using the fibre-optic hydrophone and the results compared with those obtained using a PVDF hydrophone. The acoustic power output from the hyperthermia transducer was measured using a radiation force balance. It was observed that the root mean square voltage of the fibre-optic hydrophone output is proportional to the square root of the acoustic power up to more than 80 W. It was also observed that, under continuous-wave operation, the fibre optic hydrophone can stand up to very high power (more than 200 W) without being damaged. As its sensing element is the fibre itself, whose diameter is considerably narrower than the width of the ultrasonic beam, it can provide resolution of about 80 microm in beam profile measurement. The fibre is a line sensor and a computer tomographic technique is used to recover the pressure profile from the hydrophone output voltage. In typical clinical operations, the six-transducer assembly is driven with less than 150 W of electrical power input. In such cases, each individual transducer receives less than 25 W of input power and non-linearity and generation of high frequency harmonics at the focus is not a significant problem.

Acoustics↗
PubMed1989

Photosensitive annular elastolytic giant cell granuloma with cutaneous amyloidosis.

Annular erythematous indurated plaques with central clearing developed on sun-exposed areas of a diabetic patient. The lesions were aggravated by sun exposure. Histological examination revealed features as described in annular elastolytic giant cell granuloma. In addition, subepidermal amyloid deposits were identified. Though a coincidental occurrence cannot be excluded, a possible pathogenetic relationship between the two conditions is postulated. It is believed that they are caused by actinic damage to skin altered by diabetes.

Aged↗
PubMed1988

Specific acoustic impedances of piezoelectric ceramic and polymer composites used in medical applications.

The specific acoustic impedance of the piezoelectric composites over the frequency range of 0.5-7.5 MHz was measured using the reflection, the echo-shift, and the resonance techniques. There was a significant difference between the values obtained by the reflection technique in comparison with the other two techniques. It is argued that the difference is inherent in the measurement techniques and they measure different properties of the composite such as acoustic impedance and reflectivity. The specific acoustic impedance and the reflectivity were found to be a function of the volume fraction of the ceramic and not a function of frequency.

Acoustic Impedance Tests↗
PubMed1988

Kimura's disease. Involvement of regional lymph nodes and distinction from angiolymphoid hyperplasia with eosinophilia.

The clinicopathologic features of nine patients with Kimura's disease and 15 patients with angiolymphoid hyperplasia with eosinophilia (ALHE) were studied and compared in order to clarify the confusion between these two entities. The common features shared by both conditions included male predominance, predilection for the head and neck regions, tendency to recur, and vascular nature of the lesion with lymphoid and eosinophilic infiltrates. However, Kimura's disease was usually seen in younger individuals for a longer duration and occurred as a deeply seated, large soft-tissue mass, without significant change of the overlying skin initially. In addition, it was often accompanied by peripheral blood eosinophilia and elevated serum IgE. In contrast, ALHE lesions were multiple small dermal papular or nodular eruptions observed in older patients and present for a shorter duration; they were less frequently accompanied by peripheral blood eosinophilia. The main histopathological difference was the presence of "histiocytoid" or "epithelioid" blood vessels in ALHE but not in Kimura's disease. Kimura's disease was further characterized by eosinophilic folliculolysis; IgE deposits in the germinal centers; and frequent involvement of regional lymph nodes, salivary glands, and skeletal muscles. The eosinophilic infiltration, especially the formation of eosinophilic microabscesses, along with increased number of small blood vessels, perinodal eosinophilic infiltration, and eosinophilic folliculolysis characterized the nodal involvement by Kimura's disease. Our study indicates that Kimura's disease and ALHE are two distinct clinicopathologic entities. We place particular emphasis on the involvement of regional lymph nodes in Kimura's disease. In addition, we observed Charcot-Leyden crystals and polykaryocytes in both conditions. One of the patients with Kimura's disease also had an associated nephrotic syndrome.

Adolescent↗
PubMed1988

Fixed drug eruptions--a Singapore study.

This study documents 62 patients with fixed drug eruptions (FDE) proven by provocative testing. Of these 39 (63%) were caused by tetracycline hydrochloride and 12 (19%) caused by Saridon (R). Fifty-eight (94%) of the patients had 10 or less lesions and 50 (81%) had 5 or less lesions. The lips and genitalia were preferential sites being involved in 28 (45%) and 22 (36%) instances. In 6 instances each a solitary lesion occurred on the lower lip or the glans penis. At presentation, 43 (69%) patients were unaware of the drug-induced nature of their condition. Compared with previous reports the causative drugs varied from place to place and from decade to decade. This may be due to differences in prescription patterns.

Adult↗
PubMed1988

Initial experience with the argon laser in cutaneous vascular lesions.

An 18-month clinical study on the effects of argon laser in cutaneous vascular disorders in 41 patients carried out at the National University Hospital is discussed. The results confirmed the excellent response that can be achieved in lesions such as capillary hemangiomas, granuloma pyogenicum, cherry angiomas, telangiectasias and spider angiomas, but not in venous flare of the lower limbs. We are cautiously optimistic about its role in portwine stains; results are still being assessed. Complication rates so far have been relatively low with scarring observed in one patient.

Adolescent↗
PubMed1988

Non-infective skin associations of diabetes mellitus.

A study of non-infective skin associations of diabetes mellitus was conducted on 100 consecutive outpatient diabetics over a 3-month period. 10 were insulin-dependent diabetics (IDDM), 24 insulin-requiring and 66 non-insulin dependent diabetics (NIDDM). A total skin evaluation was done for each patient with skin biopsy whenever appropriate. Twenty-three patients had diabetic dermopathy; the frequency of retinopathy in this group (39.1%) is significantly higher than that without diabetic dermopathy (6.9%) (p less than 0.001). There were 20 instances of cutaneous complications of therapy; 10 had insulin lipodystrophy (29.4% of 34 insulin users). Twelve patients, 8 of whom were overweight, had acanthosis nigricans. There were 6 Indians among them and all the patients had NIDDM. Eight had xanthelasma. Vitiligo occurred in 3.3% of those with NIDDM. Classical scleredema diabeticorum and cheiroarthropathy occurred in 2% of patients. One patient had atypical granuloma annulare. There was a higher incidence of xanthelasma in our study compared with studies done previously. Insulin lipodystrophy and acanthosis nigricans in the absence of classically described syndromes of insulin resistance seem to be fairly common phenomena and merit further investigation locally.

Adolescent↗