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Biomedical subjects

D Tan

Publications and source records attributed to D Tan.

At least 109 records · Page 6Linked to original sources
PubMed1994

Rat gastric motor response to food protein-induced anaphylaxis.

BACKGROUND/AIMS: Antigen challenge of sensitized rats leads to delayed gastric emptying, but the mechanism (gastroparesis or prolonged trituration) and mediators are unknown. METHODS: Hooded Lister rats were sensitized by intraperitoneal injection of egg albumin as antigen, and control rats were sham-sensitized. On day 14, antral manometric and antroduodenal myoelectric activities in sensitized and sham-sensitized rats were recorded in response to antigen challenge, and the contractility of gastric antral circular muscle strips (mucosa intact) in standard tissue baths was measured in response to antigen or other agents. RESULTS: In vivo, the intragastric antigen challenge of sensitized (but not sham-sensitized) rats provoked diarrhea, reduction in the antral motility index, and disruption of the duodenal migrating motor complex. In vitro, antigen induced a tonic contraction of antral circular muscle segments from sensitized animals. Doxantrazole, but not disodium cromoglycate, inhibited antigen-induced contraction. Whereas histamine, 5-hydroxytryptamine, prostaglandins, leukotrienes, and platelet-activating factor contracted gastric muscle strips, neither specific antagonists, prostaglandin synthase, or 5-lipoxygenase inhibitors inhibited antigen-induced contraction. Tetrodotoxin increased antigen-induced contraction; however, the antigen-induced contraction was unaffected by atropine, guanethidine, or NG-nitro-L-arginine methyl ester. CONCLUSIONS: Food protein-induced, immunoglobulin E-mediated delayed gastric emptying in sensitized rats is associated with a transient reduction in gastric antral contractions. Antigen-induced contraction appears to be under nonadrenergic, noncholinergic, nonnitroxinergic inhibitory neural control.

Albumins↗
PubMed1994

Intracellular glutathione influences collagen generation by mesangial cells.

The cellular redox state is altered in a number of pathological conditions, including various forms of glomerular injury and diabetes. For example, glucose, via the pentose phosphate pathway generates NADPH, which maintains glutathione (GSH) (part of a major intracellular reducing system) in its reduced state. GSH in turn influences the activity of transcription factors on gene expression. We therefore examined whether changes in cellular GSH influence total collagen synthesis and mRNA levels for collagen I, collagen IV and TGF-beta in SV-40 transformed mouse mesangial cells (MC) maintained in either 5 or 25 mM glucose media. Total intracellular GSH was increased by N-acetylcysteine (NAC; 10 mM) or decreased with the GSH synthesis inhibitor buthionine sulfoximine (BSO; 0.2 mM) in MC. NAC increased 3H-proline incorporation into collagenase-sensitive protein while BSO decreased it under both glucose conditions. The presence of BSO did not reverse the increased collagen synthesis seen in the NAC stimulated cells. Northern blot analysis showed increased mRNA levels for collagen I, collagen IV and TGF-beta in cells grown in high glucose (25 mM). NAC increased the mRNA for all three compounds while BSO alone had no effect on these mRNA levels. However, BSO reversed the increased mRNA levels for collagen I, IV and TGF-beta seen in the presence of NAC. These findings suggest that the cellular redox state may influence gene transcription in MC, and may have implications in explaining injury-associated alterations of mesangial matrix generation.

Acetylcysteine↗
PubMed1994

Both physiological and pharmacological levels of melatonin reduce DNA adduct formation induced by the carcinogen safrole.

Hepatic DNA adduct formation induced by the chemical carcinogen, safrole, was suppressed by both endogenous pineal melatonin release and by the exogenous administration of melatonin to rats. DNA damage after administration of of melatonin to rats. DNA damage after administration of 100 mg/kg safrole (i.p.) was measured by the P1 enhanced 32P-postlabeling analysis method. The RAL (relative adduct labeling) x 10(7) of carcinogen modified DNA in the liver of untreated controls and in safrole treated animals killed during the day, at night, after pinealectomy and pinealectomy plus melatonin injection (0.15 mg/kg x 4 or a total of 0.6 mg/kg) was 0, 12.6 +/- 0.75, 10.9 +/- 0.72, 13.6 +/- 1.12 and 5.7 +/- 0.53 respectively. For the same groups of animals, circulating melatonin levels at the termination of the study were 31 +/- 3, 29 +/- 2, 276 +/- 31, 24 +/- 1 and 13,950 +/- 1016 pg/ml serum respectively. The higher the melatonin concentration in the serum the lower was DNA adduct formation in the rat liver. Thus, high nocturnal levels of melatonin were protective against safrole-induced DNA damage. These findings indicate that the functional pineal gland plays an important role in oncostatic actions of carcinogens such as safrole. At physiological levels, melatonin seemed to prevent especially the formation of what was referred to as the N1 DNA adduct. Melatonin's ability to suppress DNA adduct formation may relate to its inhibitory effect on a mixed function oxidase, cytochrome p-450, and on the recently identified hydroxyl radical scavenging capacity of the indole. The oncostatic action of melatonin is also suggested by its nuclear accumulation and DNA stabilization characteristics. At pharmacological levels melatonin is extremely potent in preventing DNA modification induced by the chemical carcinogen, safrole.

Animals↗
PubMed1993

Excimer laser photorefractive keratectomy in Singapore--a new treatment modality for myopia.

BACKGROUND: Myopia is a national epidemic in Singapore. Photorefractive Keratectomy (PRK) for the treatment of myopia using the Argon Fluoride Excimer Laser commenced in January 1992 at the Singapore National Eye Centre. METHODS: An open, prospective, non randomised clinical trial to assess the efficacy, predictability, stability, and safety of PRK for the correction of myopia between -2.0 to -6.0 dioptres. RESULTS: One hundred and fifty-five eyes of one hundred and thirty-five patients underwent PRK between January and September 1992, of which thirty-one had completed at least six months of follow-up. Twenty-nine of the thirty-one patients (93.5%) achieved an unaided visual acuity of at least 6/12. Twenty-six patients (83.9%) were within 1 dioptre of emmetropia. There was an initial over-correction in all patients which regressed to a plateau at around three or four months. Corneal haze did not pose a significant problem. Three patients had ocular hypertension, and another developed a mild allergic reaction to the antibiotic-steroid ointment. CONCLUSIONS: Excimer Laser Photorefractive Keratectomy is a very effective, fairly predictable, stable and safe surgical method for the treatment of myopia.

Adult↗
PubMed1993

Personal experience of right anterior segmentectomy (segments V and VIII) for hepatic malignancies.

BACKGROUND: Right anterior segmentectomy is the most difficult type of hepatic resection to perform and is reported only rarely. For patients with tumors limited to the anterior segment but complicated by mild liver dysfunction, this is the only type of hepatectomy that can be tolerated. This article described personal experience with this operation in 17 patients with liver malignancies. METHODS: Fourteen patients had hepatocellular carcinoma, one had cholangiocellular carcinoma, and two had metastases, one from rectal and the other from gastric carcinoma. Except in one case of dense adhesion of the hepatoduodenal ligament, hemihepatic vascular occlusion was used. Both the right and middle hepatic veins were fully exposed in 14 patients. RESULTS: The average operation time was 412 minutes and the average blood loss was 1482 ml. There was one operative death as a result of pneumonia and liver failure. Another patient had prolonged bile leakage with right pleural effusion and bleeding gastric erosions. The cumulative 1- and 5-year survival rates were 88% and 47%, respectively. CONCLUSIONS: The results of this experience indicate that in selected patients with hepatic malignancies this procedure is safe and compatible with improved survival. This may be the first report to describe the clinical features and operative technique in a series of patients treated by right anterior segmentectomy.

Aged↗
PubMed1992

Dietary palmitic and oleic acids exert similar effects on serum cholesterol and lipoprotein profiles in normocholesterolemic men and women.

To compare the effects of dietary palmitic acid (16:0) vs oleic acid (18:1) on serum lipids, lipoproteins, and plasma eicosanoids, 33 normocholesterolemic subjects (20 males, 13 females; ages 22-41 years) were challenged with a coconut oil-rich diet for 4 weeks. Subsequently they were assigned to either a palm olein-rich or olive oil-rich diet followed by a dietary crossover during two consecutive 6-week periods. Each test oil served as the sole cooking oil and contributed 23% of dietary energy or two-thirds of the total daily fat intake. Dietary myristic acid (14:0) and lauric acid (12:0) from coconut oil significantly raised all the serum lipid and lipoprotein parameters measured. Subsequent one-to-one exchange of 7% energy between 16:0 (palm olein diet) and 18:1 (olive oil diet) resulted in identical serum total cholesterol (192, 193 mg/dl), low-density lipoprotein cholesterol (LDL-C) (130, 131 mg/dl), high-density lipoprotein cholesterol (HDL-C) (41, 42 mg/dl), and triglyceride (TG) (108, 106 mg/dl) concentrations. Effects attributed to gender included higher HDL in females and higher TG in males associated with the tendency for higher LDL and LDL/HDL ratios in men. However, both sexes were equally responsive to changes in dietary fat saturation. The results indicate that in healthy, normocholesterolemic humans, dietary 16:0 can be exchanged for 18:1 within the range of these fatty acids normally present in typical diets without affecting the serum lipoprotein cholesterol concentration or distribution. In addition, replacement of 12:0 + 14:0 by 16:0 + 18:1, but especially 16:0 or some component of palm olein, appeared to have a beneficial impact on an important index of thrombogenesis, i.e., the thromboxane/prostacyclin ratio in plasma.

Adult↗
PubMed1992

Effects of intravenous infusions of diaspirin cross-linked hemoglobin (DCLHb) on sheep.

The purpose of this study was to compare the cardiopulmonary, hematologic, and immunologic responses of unanesthetized sheep to single, "topload", intravenous infusions of either 10 mL/Kg or 40 mL/Kg of Diaspirin Cross-Linked Hemoglobin, 10 mL/Kg or 40 mL/Kg of a Human Serum Albumin (HSA) solution oncotically adjusted with human serum albumin to approximately match the oncotic pressure of the DCLHb, or 10 mL/Kg of Erythrocyte Hemolysate solution prepared in a manner similar to that commonly described in the literature and referred to as "stroma free hemoglobin". Solutions were infused at a rate of 1 mL/Kg/minute and animals were monitored for 72 hours after infusion. These studies demonstrated that in sheep infusion of either DCLHb or HSA solutions was well tolerated and did not produce a significant increase in plasma C3a levels, an increase in the plasma concentration of thromboxane B2, or unexpected fluid shifts. In contrast, infusion of the Erythrocyte Hemolysate produced a greater than 10-fold increase in plasma C3a concentrations, a greater than 6000-fold increase in plasma TxB2 concentration, significant fluid shifts, and changes in a variety of other parameters consistent with induction of a dramatic inflammatory response. These results indicate that appropriately prepared and purified DCLHb solutions do not elicit an inflammatory reaction in sheep.

Animals↗
PubMed1992

Treatment of fever due to exopathic wind-cold by rapid acupuncture.

57 cases of common cold, influenza, acute tonsillitis and acute bronchitis were treated by rapid needling with filiform needles at Dazhui (Du 14), Fengchi (GB 13), and Quchi (LI 11). The indices for observation were first determined, and the 19 cases that manifested an axilla temperature drop of over 1 degree C after treatment and a ratio of < 0.3 of the main symptom scores after treatment were regarded as markedly effective; the 27 cases that manifested an axilla temperature drop of 0.5-1.0 degree C and a symptom score ratio of 0.3-0.6 were regarded as effective, and the 11 cases that manifested an axilla temperature drop of < 0.5 degrees C and a symptom score ratio of > 0.7 were regarded as failures. The total effective rate was 80.7%. Analysis of the individual patients indicated that the peripheral blood leucocyte and lymphocyte counts differed insignificantly after needling, while the body temperature, rate of respiration, pulse, blood pressure and acupoint temperature all dropped, with a simultaneous increase in the percentage of T-lymphocytes. The immediate effects were especially marked in fevers due to exogenous wind and cold.

Acupuncture Therapy↗
PubMed1991

Successful treatment of tuberculous peritonitis while maintaining patient on CAPD.

Although conventional wisdom advises removal of the Tenckhoff catheter as part of the therapy for tuberculous peritonitis, there are a few recent reports of cases successfully treated while maintaining the patients on CAPD. We wish to report three cases treated without interrupting CAPD. In two of the patients, cultures were positive for Mycobacterium tuberculosis and in the third case, although the cultures were negative, the patient improved on anti-Tb medications. Smear for AFB was positive in one patient; and two had a positive PPD. All had predominance of lymphocytes and monocytes in effluent. The total WBC count was 160-300 and two patients had fever. All had abdominal pain. One patient was treated with INH and ethambutol; one with INH and rifampin and one (who was suspected of being HIV+) also received pyrazinamide (PZA) until culture was available. Cultures grew in 4-6 weeks. All were started on therapy prior to having the culture results, and all showed clinical improvement within two weeks. One patient had his catheter replaced two months later because of pseudomonas peritonitis, continued on CAPD for an additional five months, then changed to HD because of recurrent bacterial peritonitis. One patient died of complications of diabetic vascular disease three months later with no evidence of peritonitis. One patient has remained on anti-Tb treatment for seven months and is doing well on CAPD.

Adult↗
PubMed1990

The impact of CAPD treatment on lipid metabolism and cardiovascular risk.

The metabolism of lipids in CAPD has not been fully elucidated. To further clarify the behavior of dyslipidemia in this setting we followed the values of total cholesterol (TC), HDL-cholesterol (HDL-C) and apolipoprotein (apo) parameters over time (12-24 months) in 40 patients and correlated these values and their ratios with clinical (age, gender, race, weight, diabetes, etc.) and biochemical (multiphastic screen) information. Mean HDL-C was lower in men (p less than 0.04), in whites, (p less than 0.03) and in diabetic patients (p less than 0.05), but there were no group differences for mean total cholesterol, mean apolipoprotein values, the atherogenic risk ratio TC/HDL-C, or the anti-atherogenic ratio apo A-I/apo B. Total months on CAPD was found to correlate positively with TC/HDL-C (p less than 0.05), an atherogenic risk factor, and to correlate negatively with HDL-C (p less than 0.02), an anti-atherogenic index. There was also a negative correlation with another anti-atherogenic index, apo A-I/apo B, which did not reach statistical significance (r = -0.41, p = NS). Counterbalancing this apparently increased atherogenic risk is the stability of individual parameters for each patient over time in this study. In fact, the good news appears to be that TC, HDL-C, apolipoproteins and the risk ratios TC/HDL-C and apo A-I/apo B all remained stable over 12-24 months (p = NS by paired t-test for all). Thus, we find no evidence for worsening of the uremic dyslipidemia over time with CAPD treatment.

Apolipoproteins↗
PubMed1987

Treadmill exercise testing in ischaemic heart disease.

An analysis of 1,600 consecutive treadmill exercise tests is made, with emphasis on those with an ischaemic response. An ischaemic response is defined as a horizontal or downsloping depression of the ST segment of 1 mm or more. A hypertensive response is recorded where the blood pressure exceeds 200 mm Hg systolic or 100 mm Hg diastolic during exercise. There were 150 (9%) ischaemic responses and 279 (17%) hypertensive responses. Cardiac arrhythmias were detected in 173 (11%) subjects. Among the 150 subjects with ischaemic responses, 69 (46%) of them presented with anginal symptoms while 64 (43%) of them had no precordial pain. Twenty-seven (18%) of them had definite previous myocardial infarction. Risk factors observed included hypertension in 54 (36%) subjects, diabetes mellitus in 33 (22%) subjects, hypercholesterolaemia in 41 (37%) out of 112 subjects and 44 (29%) cigarette smokers.

Adult↗
PubMed1980

Clinical aspects of treadmill exercise testing.

A study is made of 525 consecutive treadmill exercise tests. Horizontal or downsloping ST segment depression of 1 mm or more was considered or ischaemic response. A systolic blood pressure exceeding 200 mm Hg or a diastolic blood pressure exceeding 100 mm Hg during or after exercise was defined as a hypertensive response. An ischemic response was found in 48 subjects. In this group, 7 (15%) had previous myocardial infarction, 10 (21%) had minor ischaemic changes in the resting electrocardiogram. Twenty-eight (58%) complained of precordial pain or discomfort. A hypertensive response occurred in 101 subjects. Thirty-eight of them had precordial pain or discomfort. The resting blood pressure was elevated in 52, borderline in 32, and normal in 17 subjects. Cardiac arrhythmias were detected in 53 patients. Other abnormalities detected included 3 cases of hypertrophic cardiomyopathy and 1 case of post exercise bronchospasm due to propranolol.

Adolescent↗