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Biomedical subjects

G H Tan

Publications and source records attributed to G H Tan.

28 records · Page 2Linked to original sources
PubMed1991

Tussock moth dermatitis: evidence for histamine involvement.

Moth hairs shed by the few tussock moths caught during the first documented outbreak of pruritic dermatitis in Singapore were investigated to provide evidence for the presence of histamine. Aqueous extract of the moth hairs was used for the test and analyses. In the isolated guinea pig ileum, the extract, like histamine, produced responses that were blocked by mepyramine. The high performance liquid chromatographic (HPLC) analysis of the fluorescamine derivative of the moth extract resulted in a fluorescent peak with exactly the same retention. time as the histamine fluorescamine derivative. The mass spectrum of the pentafluoropropionic acid (PFP) derivative of the extract was also identical to that obtained from the reference histamine-PFP derivative. We concluded that histamine was present in the tussock moth hairs and was involved as one of the inflammatory mediators responsible for the pruritic skin rashes.

Animals↗
PubMed1986

Nickel sensitivity in Singapore.

Nickel is the most common cause of allergic contact dermatitis in Singapore, resulting in positive reactions in patch tests between 7 and 14%. Women are more commonly affected and have an earlier mean age of onset than men (21 compared with 32). Wrist watches, earrings, buttons, and necklaces are the common source of nickel allergy. Twenty-five percent of patients also had some form of associated hand eczema. Thirty-six percent of patients had a history of atopy showing a higher incidence than the normal populations. Thirty-seven percent of patients had an associated positive reaction to cobalt.

Adolescent↗
PubMed1980

Active products of porcine trypsin after autolysis.

Porcine trypsin obtained from pancreas residues subsequent to insulin removal undergoes autolysis when subjected to chromatography and gives rise to new forms of autolyzed products with intra-chain split at bonds Lys145-Ala146 and Arg105-Val106. Incubation of 1% solutions of porcine trypsin either at pH 5.0 or at pH 9.1 induces autolysis to give active products involving one or two specific cleavages of bonds Lys145-Ala146 and Arg105-Val106 or Lys131-Ser132, as well as inactive degraded products. No evidence has been obtained that on autolysis of porcine trypsin, and active fragment with molecular weight lower than that of the parent molecule was identified. The active forms of autolyzed products of porcine trypsin have almost the same specific activity as the intact enzyme when assayed against BAEE. They are of the same molecular weight as the parent molecule. These findings indicate that that active forms of autolyzed products maintain the specific three-dimensional structure essential for the catalytic activity of the trypsin molecule.

Amino Acid Sequence↗
PubMedDate not supplied

Solitary thyroid nodule. Comparison between palpation and ultrasonography.

OBJECTIVE: To determine the accuracy of clinical palpation in the diagnosis of solitary thyroid nodule in comparison with ultrasonographic findings. METHODS: From a computerized database of 1774 patients with the diagnosis of nodular thyroid disease made from January 1990 through December 1991 at our institution, we retrieved and reviewed the medical records of the 193 patients who underwent ultrasonography of the thyroid (42 patients with multinodular glands on palpation were excluded). Nodules were categorized as "solitary" or "dominant nodule of a multinodular gland." Concordance rates were measured between results of palpation and ultrasonographic findings. RESULTS: Of 151 patients included in the study, 78 had solitary nodules on ultrasonography and 73 had multiple nodules. Of those with multiple nodules, 49 had two nodules and 24 had three or more nodules. Of clinically palpable nodules, 89% were 1 cm or greater in diameter. In 72% of the patients with multiple nodules, the other nodules not identified on palpation were less than 1 cm in diameter. The overall concordance rate between the size of the solitary nodule or the dominant nodule in a multinodular gland estimated with clinical palpation and the actual size seen on ultrasonography was 72%. The relationship between multiple nodules and malignancy was not statistically significant. CONCLUSIONS: Our results suggest that (1) a palpable solitary nodule represents a multinodular gland in about 50% of patients, (2) clinical palpation is less sensitive than thyroid ultrasonography in identifying multiple nodules, and (3) palpation is reliable only if a nodule is at least 1 cm in diameter. We recommend that small, occult (impalpable) thyroid nodules not be considered clinically important; they do not warrant further evaluation unless ultrasonographic features suggest malignancy or the nodule increases in size.

Adult↗
PubMedDate not supplied

Recurrent hyperthyroidism after radioiodine-induced hypothyroidism: report of two cases and literature review.

The practice at the Mayo Clinic in treating Graves' disease with radioiodine (131 I) is to achieve a hypothyroid state. Less than 10% of the patients need more than one dose. Although cases of transient hypothyroidism have been reported after treatment with 131 I, the recurrence of hyperthyroidism is unusual after hypothyroidism has been induced with 131 I. We studied two cases seen at our institution in the past year in which the circumstances behind the recurrence have never been reported previously. The first case illustrates a recurrence of hyperthyroidism after the patient had received 38.5 mCi of 131 I. The second patient had recurrence of hyperthyroidism after 22 years of replacement therapy with levothyroxine. Both patients had increased levels of thyroid-stimulating immunoglobulin. We believe that the recurrence of the hyperthyroid state in these two patients was due to incomplete ablation of the thyroid. Apparently 131 I caused hypothyroidism, but residual cells remained viable and under continuous stimulation of thyroid-stimulating immunoglobulin produced recurrent thyrotoxicosis.

Journal Article↗
PubMedDate not supplied

Transient hypopituitarism.

Spontaneous recovery of pituitary function in patients with hypopituitarism is rare. We report the case of a 30-year-old man in whom hypopituitarism and sudden onset of bilateral hearing loss developed after a viral infection. No evidence of a mass lesion was detected on computed tomography or magnetic resonance imaging of the pituitary gland. The patient received a 3-week course of treatment with a high dose of glucocorticoids; in a period of 6 weeks, he felt clinically well, and biochemical tests showed spontaneous return of normal anterior pituitary function. We speculate that an immune response triggered by the viral infection initiated an inflammatory process that involved the hypothalamus or pituitary gland and caused the hypopituitarism. The treatment with high-dose glucocorticoids could have prompted the resolution of the hypothalamic-pituitary inflammatory process and facilitated spontaneous recovery of pituitary function. This case shows that hypopituitarism may be transient an outcome that should be considered in patients with idiopathic hypopituitarism.

Journal Article↗
PubMedDate not supplied

Amiodarone-induced hyperthyroidism and a thyroid nodule.

OBJECTIVE: To report two cases of thyrotoxicosis associated with amiodarone therapy and to discuss how the presence of a thyroid nodule alters management. METHODS: We describe two patients with amiodarone-induced hyperthyroidism, review the mechanisms of disease, and outline a strategy for decision making relative to treatment in the presence of a thyroid nodule. RESULTS: Amiodarone-induced thyrotoxicosis occurs by two mechanisms: a direct toxic effect and iodine loading. This condition may be treated medically or surgically, but when discontinuation of amiodarone therapy is not possible and medical management is ineffective, surgical therapy is often necessary. The optimal presurgical management in the cases described required the use of thyroid scanning to determine whether the disease process was attributable to a hyperfunctioning nodule or generalized. The findings were helpful in planning the extent of surgical excision. CONCLUSION: When surgical treatment is planned for patients with a solitary thyroid nodule and amiodarone-induced hyperthyroidism, preoperative thyroid scanning will direct the surgeon to perform either subtotal thyroidectomy for diffuse disease or lobectomy for a hyperfunctioning nodule.

Journal Article↗