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Biomedical subjects

S Lam

Publications and source records attributed to S Lam.

At least 127 records · Page 7Linked to original sources
PubMed1991

Desferrioxamine ameliorates retinal photic injury in albino rats.

Albino rats were given intraperitoneal desferrioxamine before exposure to intense fluorescent light. Morphometric and morphologic studies of the retina indicated that there was better preservation of photoreceptor nuclei and fewer subretinal macrophages in rats treated with desferrioxamine than in the control rats. The results of the study imply that iron and hydroxyl radicals may be important mediators in photic retinal injury.

Animals↗
PubMed1991

Lamellar corneal autograft for corneal perforation.

A corneal perforation developed in the right eye of a 46-year-old man after removal of a corneal foreign body. Two attempts to seal the perforation with cyanoacrylate glue failed. The patient subsequently underwent lamellar corneal autograft, which successfully closed the perforation. To the best of our knowledge, this is the first report of repairing a corneal perforation with lamellar corneal autograft.

Corneal Injuries↗
PubMed1990

Amelioration of retinal photic injury in albino rats by dimethylthiourea.

Light-induced formation of oxygen free radicals has been proposed as the underlying mechanism of photic retinal injury. We investigated the role of hydroxyl radical in retinal photic injury by treating dark-adapted albino rats with intraperitoneal dimethylthiourea 3 hours before exposure to intense fluorescent light. Dimethylthiourea is a specific antioxidant against hydroxyl radical. We demonstrated that dimethylthiourea penetrates well into retinal tissue and has a half-life of approximately 19 hours. Morephologic differences between the control and dimethylthiurea-treated rats were not remarkable 6 hours after light exposure, but they became significant 6 and 14 days after light exposure. Morphometric studies showed that there was significantly better preservation of photoreceptor nuclei in dimethylthiourea-treated rats 6 and 14 days after light exposure. Rhodopsin levels were significantly higher in the dimethylthiourea-treated rats 6 hours and 14 days after light exposure, while rhodopsin levels were comparable in the control and dimethylthiourea-treated rats 6 days after exposure. The differences in morphometry and rhodopsin levels between the control and dimethylthiourea-treated rats were statistically significant in relationship to dimethylthiourea treatment. The superior and temporal retinal quadrants appeared most vulnerable to photic injury in control rats 6 and 14 days after light exposure. These findings indicate that dimethylthiourea ameliorates retinal photic injury, and that hydroxyl radical plays an important role in mediating retinal photic injury.

Animals↗
PubMed1990

High performance liquid chromatographic assay of Amicar, epsilon-aminocaproic acid, in plasma and urine after pre-column derivatization with o-phthalaldehyde for fluorescence detection.

A simple, reliable and highly sensitive procedure was devised for measuring the levels of Amicar in blood and urine. 100 microL of serum or urine sample was added to 10 microL of a 10% w/v zinc sulfate solution and 100 microL of methanol, as previously described (Lam et al., 1980) for the removal of proteins by precipitation. 50 microL of the supernatant was then mixed with 300 microL of 1 M borate buffer containing D-valine as the internal standard before derivatization with o-phthalaldehyde. The amino acids were then separated by a stereoselective reversed-phase system using a mobile phase containing 10% of acetonitrile in 2.5 mM Cu(II) complexes of L-proline. The chromatography is highly selective, resolving Amicar from L-valine which in turn is resolved from its unnatural D-antipode, the internal standard. The procedure including sample preparation and separation required a total of 15 min. As little as 50 ng/mL of Amicar in body fluids could be detected as the o-phthalaldehyde derivative by fluorescence.

Aminocaproic Acid↗
PubMed1990

Person-to-person transmission of cholera in a psychiatric hospital.

An outbreak of cholera caused by Vibrio cholerae O1, biotype el tor, serotype Ogawa, phage type 4, was reported in a psychiatric hospital in Singapore. A total of 74 inmates (18 symptomatic and 56 asymptomatic) were infected; two of them died. Extensive epidemiological investigations showed that the organism was not transmitted by contaminated food or water but through close person-to-person contact. Early recognition of the outbreak and prompt implementation of epidemic control measures comprising surveillance of diarrhoea, rectal swabbing of all asymptomatic inmates, isolation of those found to be infected, maintenance of a high standard of environmental sanitation and mass chemoprophylaxis with doxycycline, rapidly brought the outbreak under control.

Adult↗
PubMed1990

The effects of low density lipoproteins on uptake of Photofrin II.

The cellular uptake of Photofrin II (PII) was studied using fluorescence imaging and chemical extraction. The influence of serum and low density lipoproteins (LDL) was examined under a variety of experimental conditions employing cultured human cells of different origins as well as a subcutaneously SMT-F tumor implanted in mice. Results showed that serum inhibited PII uptake. In general, LDL also inhibits PII uptake with the exception of an initial increase in the first 10-30 min when the cellular concentration of PII was measured by fluorescence imaging instead of chemical extraction. Our results suggest a possible de-aggregation process occurring upon internalization or binding of PII to LDL.

Animals↗
PubMed1990

Chloramphenicol concentrations in sera of patients with typhoid fever being treated with oral or intravenous preparation.

Serum chloramphenicol and chloramphenicol succinate concentrations in patients given equivalent doses of chloramphenicol base either intravenously or orally for typhoid fever were measured by high-performance liquid chromatography. The mean serum chloramphenicol concentrations were significantly lower in the 11 patients treated with intravenous chloramphenicol succinate than in the 15 patients treated with oral chloramphenicol capsules.

Administration, Oral↗
PubMed1990

Detection of early lung cancer using low dose Photofrin II.

Fluorescence imaging using hematoporphyrin derivative (HpD) or Photofrin II as a tumor marker has been used for localization of early bronchogenic carcinoma. Wider clinical application of HpD or Photofrin II as a cancer imaging agent has been hampered by the potentially serious and prolonged skin photosensitivity. Using a sensitive fluorescence bronchoscope system with a ratio fluorometer probe, carcinoma in situ was detected in four patients with low dose Photofrin II (0.25 mg/kg) with no apparent skin phototoxicity to 30 J/cm2 visible light on skin photosensitivity test.

Aged↗
PubMed1990

Response to allopurinol pretreatment in a swine model of heart-lung transplantation.

The role of allopurinol in the prevention of ischemia-reperfusion injury was assessed in a model of heart-lung transplantation. Fourteen swine were divided into two groups (seven donors and seven recipients). All heart and lung blocks were placed in hypothermic storage after perfusion with cold iso-osmolar cardioplegic solution and modified Collins solution, respectively (t = 8-10 degrees C for heart and t = 16-18 degrees C for lungs). The total ischemic time including the orthotopic transplantation was 6 h. Animals (donors and recipients) were pretreated with allopurinol given orally at a dosage of 50 mg/kg for 4 days. Animals were assessed by monitoring heart and lung function, including extravascular lung water at three time intervals, which included pretransplantation (donor), and 30 min and 2 h posttransplantation (recipient). Erythrocyte peroxidation susceptibility was assessed for 3 days, and surgery was performed on day 4. The malondialdehyde levels determined from erythrocyte exposure to in vitro peroxidative challenge classified three paired donor and recipient animals as responders and four paired donor and recipient animals as nonresponders to the allopurinol pretreatment. A persistent deterioration of lung function was observed over time in nonresponders (p less than .05) (increase of lung water, decrease of partial pressure of oxygen, increase in alveolar-arterial gradient, and decrease in arterial-alveolar tension ratio). Responders showed no significant alterations in lung function. This study in swine, a species devoid of myocardial xanthine oxidase activity, indicates that allopurinol may have a mechanism of action other than xanthine oxidase inhibition in the prevention of ischemia-reperfusion injury. The parallelism between protection of lung function and of red blood cells suggests the involvement of a generalized increase in tissue antioxidant capacity.

Allopurinol↗
PubMed1989

Histamine and leukotrienes release in bronchoalveolar fluid during plicatic acid-induced bronchoconstriction.

Bronchoalveolar lavage (BAL) was performed before and 10 minutes after inhalation challenge with plicatic acid in five patients with red cedar asthma. There was a significant release of histamine and leukotriene E4 into the BAL fluid in all the patients after challenge. Inhalation challenge with methacholine in six patients with nonoccupational asthma and inhalation challenge with plicatic acid in two subjects without asthma did not result in the release of mediators in the BAL fluid. These studies provide direct evidence that plicatic acid-induced bronchoconstriction was accompanied by increased levels of histamine and leukotriene E4 release, whereas a nonimmunologic induction of bronchoconstriction did not induce such local mediator release. BAL may provide a useful means of studying the pathogenesis of occupational asthma caused by exposure to low-molecular-weight compounds.

Adolescent↗
PubMed1989

Atonic pupil after cataract surgery.

A dilated, atonic pupil is a recognized but unusual complication of cataract surgery. It appears to be a more common occurrence than the paucity of previously published reports would suggest. In this article, seven cases of post-cataract extraction atonic pupil are described. All patients underwent uneventful cataract extraction with posterior chamber intraocular lens (IOL) implantation. In all except one patient, there was a delay from the time of surgery to the development of the atonic pupil. Pharmacologic testing demonstrated that the site of the lesion was the iris sphincter. Possible pathogenic mechanisms are discussed.

Aged↗
PubMed1989

Assay of flecainide in serum by high-performance liquid chromatography after microscale protein precipitation.

Flecainide is a new drug that is effective for the treatment of ventricular arrhythmias. Optimal therapeutic response is obtained with serum levels maintained in the 200-1000 ng/ml range. To measure flecainide in this concentration range, a high-performance liquid chromatography procedure was devised using the rapid and convenient microscale protein precipitation procedure described previously by Lam et al. to prepare the specimen for chromatography. The drug in the supernatant was injected into a Nucleosil-5,C18 reversed phase column and eluted in 5 min with a mobile phase containing 300 ml of acetonitrile, 1 ml of phosphoric acid, and 0.5 ml of diethylamine in 1 L of distilled water at a flow rate of 2 ml/min. Flecainide was detected with a Perkin Elmer 650-10 LC fluorescence spectrophotometer at 370 nm upon excitation at 285 nm. It was resolved from the endogenous compounds found in serum and from the common cardiac drugs, which eluted close to the solvent front. Peak height was proportional to flecainide levels from 120 to 1200 ng/ml. A detection limit of 30 ng/ml with signal-to-noise level better than 5 is achieved. A coefficient of variance of less than 5.0% is obtained without an internal standard.

Acetonitriles↗