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Biomedical subjects

K Wong

Publications and source records attributed to K Wong.

At least 145 records · Page 8Linked to original sources
PubMed1993

Cancer: To tell or not to tell?

After a patient is diagnosed with a malignant illness, the physician is often left with the dilemma of how to communicate the diagnosis to the patient and the family. In the West, it is often the consensus that the patient be told. This is not necessarily true elsewhere, eg in Japan, the patient is often not told. A questionnaire survey was done to study how Singapore doctors feel about revealing the diagnosis of cancer to the patient. 90.4% of respondents will reveal the diagnosis to the family, while only 43.6% will inform the patient. The possible reasons are discussed.

Attitude of Health Personnel↗
PubMed1993

Magnetic resonance imaging determination of left ventricular mass: junior Olympic weightlifters.

The relationship between left ventricular mass (LVM) and peak VO2 in junior elite Olympic-style weightlifters and sedentary subjects was investigated. Ten male weightlifters (mean +/- SE, age = 17.5 +/- 0.4 yr, wt = 72.9 +/- 3.3 kg) and 15 sedentary males (age = 18.8 +/- 0.4 yr, wt = 69.6 +/- 2.0 kg) served as subjects. Peak VO2 was measured using a continuous, incrementally loaded bicycle ergometry protocol. LVM was measured using magnetic resonance imaging techniques. Absolute peak VO2 was not significantly different (P > or = 0.05) between the weightlifters and the control subjects (3.5 +/- 0.1 vs 3.3 +/- 0.11.min-1). Absolute LVM (g) was significantly (P < or = 0.05) correlated to absolute peak VO2 (1.min-1) in the weightlifters (r = 0.723), but not in the control subjects. No other correlations between LVM in absolute or normalized by body weight, body surface area, or fat free mass terms, and absolute peak or normalized by body weight peak VO2 were significant. The weightlifters absolute LVM was significantly greater (P < or = 0.05) than that of the controls (208.1 +/- 10.0 vs 179.7 +/- 8.4 g). LVM normalized by body weight and body surface area but not by fat free mass, was significantly greater (P < or = 0.05) in the weightlifters than the control subjects. These data indicate that LVM in junior elite weightlifters is greater than that of control subjects and absolute LVM is related to absolute peak VO2 in weightlifters but not control subjects.

Adipose Tissue↗
PubMed1992

The influence of cholesterol 3-sulphate on phase behaviour and hydrocarbon order in model membrane systems.

Cholesterol 3-sulphate (CS) is a component of the intercellular lipid found in the uppermost layer of human epidermis (the 'stratum corneum') and is thought to play an important role in tissue cohesion. In this investigation we have compared the influence of cholesterol (CH) and CS on the gel-to-liquid crystalline phase behaviour, the polymorphic phase behaviour, and the hydrocarbon order profile in selected model membranes. It is shown that in sphingomyelin (SPM) systems, the presence of equimolar amounts of either CH or CS eliminates the gel-to-liquid crystalline transition as detected by calorimetry. Similarly, in 1-palmitoyl,2-oleoyl-phosphatidylethanolamine (POPE) dispersions containing a perdeuterated palmitoyl chain (POPE-d31), it is shown that both CH and CS exert an ordering effect as determined by 2H-NMR techniques, however, CS is less potent at temperatures both above and below that of the main transition for the native phospholipid. Alternatively, in mixed systems containing dioleoylphosphatidylethanolamine (DOPE) and SPM (DOPE/SPM, 6:1 mol/mol) CH promotes thermotropic L alpha-->HII phase transitions, whereas CS stabilizes the bilayer organization. These bilayer stabilization effects can be diminished by addition of Ca2+. These effects are consistent with a larger area per molecule of CS as compared to CH, presumably related to the presence of the negatively charged sulphate moiety of CS.

Cell Membrane↗
PubMed1992

Staurosporine clamps cytosolic free Ca2+ concentrations of human neutrophils.

The present studies indicate that 50 nM-10 microM-staurosporine increased cytosolic free Ca2+ concentrations ([Ca2+]i) of fura-2-loaded neutrophils in a non-linear manner. The rise in [Ca2+]i was rapid, reaching a plateau (e.g. to 0.4 microM with 1 microM-staurosporine) within 30 s, and was maintained for more than 20 min. Pretreating cells with pertussis toxin had no effect on this reaction. The elevation of [Ca2+]i was insensitive to extracellular Ca2+ concentrations and was due entirely to mobilization of intracellular Ca2+ stores. Mn(2+)-quench studies confirmed the absence of Ca2+ influx. No Ca2+ efflux occurred in staurosporine-treated cells. In combination studies, staurosporine potentiated Ca2+ influx induced by N-formylmethionyl-leucyl-phenylalanine (FMLP) and did not block Ca2+ efflux associated with peptide stimulation of neutrophils. Studies with permeabilized cells showed that staurosporine did not directly release intracellular Ca2+ stores, nor did it affect the sequestration of Ca2+ by a Ca2+/ATPase pump. A radioligand-binding assay failed to detect changes in the level of inositol 1,4,5-trisphosphate in neutrophils incubated with less than or equal to 1 microM-staurosporine, but in cells treated with 10 microM-staurosporine the assay recorded a transient increase in this second messenger similar to that induced by FMLP. Finally, lysozyme, but not beta-glucuronidase, was released from staurosporine-treated cells. The present results suggest that staurosporine increased [Ca2+]i by indirectly mobilizing internal Ca2+ stores. Staurosporine suppression of Ca2+ efflux and generation of a persistent signal may account for the maintained elevation of [Ca2+]i.

Alkaloids↗
PubMed1992

Competition between cell-substratum interactions and cell-cell interactions.

Clusterin, a glycoprotein which elicits the aggregation of a wide variety of cells (Fritz, I. B., and Burdy, K.:J. Cell Physiol., 140:18-28, 1989), has been utilized to investigate some of the factors modulating the competition between cell-substratum interactions and cell-cell interactions. We compared the responses to clusterin by anchorage-independent cells (erythrocytes) with those by anchorage-dependent TM4 cells (a cell line derived from neonatal mouse testis cells). Cells were maintained in culture in the presence of various substrata chosen to enhance cell-substratum interactions (laminin-coated wells), or to diminish cell-substratum interactions (agarose-coated wells). Results obtained showed that the aggregation of erythrocytes elicited by clusterin was independent of the nature of the substratum. In contrast, clusterin addition resulted in aggregation of anchorage-dependent TM4 cells only when TM4 cell-substratum interactions were weak. Thus, clusterin did not aggregate TM4 cells plated upon a laminin substratum, but readily aggregated TM4 cells plated upon an agarose-coated substratum, independent of the sequence of addition of cells and clusterin to the culture dish. We utilized YIGSR, a peptide which competes with laminin for laminin receptors, to determine the possible role of laminin receptors on TM4 cells in the competition between cell-substratum interactions and cell-cell interactions. The presence of YIGSR did not alter responses of erythrocytes to clusterin under all conditions examined. In contrast, the responses of TM4 cells to clusterin were greatly changed. YIGSR addition resulted in the inhibition of aggregation of TM4 cells otherwise elicited by clusterin. YIGSR also prevented attachment of TM4 cells to a laminin-coated surface, but this was reversed by the presence of clusterin. We discuss the possible roles of clusterin and laminin in altering the balance in the competition between cell to cell interactions and cell to substratum interactions.

Animals↗
PubMed1992

Surgical management of invasive pulmonary aspergillosis in immunocompromised patients.

The treatment of haematological malignancies with intensive chemotherapy and bone marrow transplantation results in prolonged periods of immunosuppression. This is associated with an increased incidence of invasive pulmonary aspergillosis (IPA) with reported mortalities of 67-83%. The mainstay of treatment is medical therapy, surgery being reserved for patients with haemoptysis. Resection of focal sites of infection has not been routinely considered in view of the high morbidity and mortality reported from the surgery of aspergillomas in past series. After the death of two neutropenic patients from massive haemoptysis following IPA in 1986, we have resected localised pulmonary aspergillus lesions in 16 patients following IPA. Five patients had haemoptysis. The most common procedure performed was a lobectomy. All patients were granulocytopenic and excessive post-operative bleeding occurred in three patients, one of whom required a re-thoracotomy as a result. There was one post-operative death due to cytomegalovirus pneumonia. Surgery was otherwise uneventful. There were no recurrent pulmonary aspergillus infections on follow-up and three patients proceeded to bone marrow transplantation. The success of surgical resection encourages an aggressive policy in the management of IPA to prevent life-threatening haemoptysis and to allow patients to proceed with further chemotherapy and bone marrow transplantation.

Adolescent↗
PubMed1992

Angiomyolipoma of the kidney: a clinical enigma in diagnosis and management.

Renal angiomyolipomas are uncommon benign tumours which clinically mimic renal cell carcinoma. They have characteristic features on ultrasound and CT scanning which may enable their diagnosis preoperatively. We review our experience of six cases of renal angiomyolipoma. These cases highlight the difficulties in making a preoperative diagnosis despite the use of modern scanning. We advocate conservative resection when the diagnosis is made preoperatively and when technically possible, but radical nephrectomy should be performed if there is a possibility of a carcinoma.

Adult↗
PubMed1991

Differential effect of diltiazem and TA-3090 on calcium homeostasis of neutrophils.

The effects of diltiazem and TA-3090, an 8-chloro analog of diltiazem, on cellular responses and calcium homeostasis of human neutrophils were investigated. TA-3090, at 10 to 20 microM, enhanced lysozyme release and superoxide generation induced in neutrophils by n-formyl-methionyl-leucyl-phenylalanine (FMLP). Higher concentrations of TA-3090 inhibited responses at IC50s between 70 and 85 microM. Diltiazem by comparison inhibited responses at an IC50 of about 200 microM. The two drugs had little or no effect on early signaling events: inositol 1,4,5-trisphosphate formation triggered by FMLP was not affected. Moreover, 500 microM TA-3090 or diltiazem did not significantly affect FMLP-triggered Ca2+ transients. (Cytoplasmic free Ca2+ levels ([Ca2+]i) were monitored in fura-2-loaded neutrophils.) Diltiazem alone caused a limited influx of extracellular Ca2+ which increased basal [Ca2+]i by twofold. Internal Ca2+ stores were not released. TA-3090, in contrast, induced a biphasic rise in [Ca2+]i--an initial mobilization of intracellular Ca2+ stores was followed after 10-15 min by a persistent influx of extracellular Ca2+ which increased [Ca2+]i to 1.3 +/- 0.7 (SD) microM. Complementary studies with semipermeabilized neutrophils showed that TA-3090 but not diltiazem directly released Ca2+ from intracellular stores. In TA-3090-treated cells, lactate dehydrogenase release was correlated with delayed influx of extracellular Ca2+. The chelation of extracellular Ca2+ by EGTA prevented LDH release. Present results show that TA-3090 and diltiazem initially blocked cell signaling at steps subsequent to phospholipase C activity. With TA-3090-treated cells, elevated [Ca2+]i ensuing from prolonged incubations likely activated inappropriate reactions leading to cell lysis and death.

Calcium↗
PubMed1991

Clustering of erythrocytes by fibrinogen is inhibited by carnitine: evidence that sulfhydryl groups on red blood cell membranes are involved in carnitine actions.

Carnitine is bound by intact red blood cells, by red blood cell ghosts, and by glutaraldehyde-fixed human erythrocytes in a non-saturable, temperature-dependent manner. Binding of carnitine by these preparations is blocked by sulfhydryl reagents. Incubation or preincubation of red blood cell preparations with carnitine inhibits the aggregation of erythrocytes otherwise elicited by fibrinogen. Identical effects are obtained with red blood cell ghosts. In contrast, choline, even at high concentrations, is inactive in preventing the aggregation of erythrocytes. We discuss possible mechanisms by which carnitine favors the dispersion of red blood cells, and we present data indicating that sulfhydryl groups on erythrocyte membranes are required to permit these carnitine actions to be manifested.

Carnitine↗
PubMed1991

Effect of dietary fat on Ito cell activation by chronic ethanol intake: a long-term serial morphometric study on alcohol-fed and control rats.

We studied the effects of long-term ethanol ingestion and dietary fat on Ito cell activation morphometrically in rats. Sixteen pairs of Wistar male rats were divided into two groups, one fed tallow and the other fed corn oil as the source of dietary fat. Each group of rats were pair-fed a nutritional adequate liquid diet containing either corn oil (CF) or tallow (TF) as fat as well as protein and carbohydrate. Half of each group received ethanol, the rest were pair-fed isocaloric amounts of dextrose via an implanted gastric tube for up to 5 months. Morphometric analysis of the change in fat and rough endoplasmic reticulum (RER) of Ito cells was performed on electron micrographs obtained from monthly biopsies including baseline. Ito cell activation was assessed by a decrease in the ratio of fat/RER in Ito cells. The ratio of fat/RER in Ito cells of alcoholic rats fed the CF diet (CFA) gradually decreased. The ratio was found to be lower than in the pair-fed control rats (CFC) at 5 months of feeding. CFA: 1.74 +/- 0.57, vs. 7.46 +/- 2.05, respectively, p less than 0.05, mean +/- SE). Ito cell fat also significantly decreased at 5 months of feeding (p less than 0.05). The fat/RER ratio in CFA significantly decreased only subsequent to the development of fatty change, necrosis, and inflammation followed by fibrosis of the liver. In contrast, the TFA rats did not show a significant decrease in the fat/RER ratio in the Ito cells throughout the study, while TFC rats showed an increase in the fat/RER ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Postprandial hypergastrinaemia in patients with colorectal cancer.

Gastrin is trophic to colon cancers that possess gastrin receptors. Whether fasting serum gastrin concentrations are high in patients with colon cancer is controversial. We therefore studied the effect of food on serum gastrin concentrations in patients with colon cancer and control subjects. Fasting serum gastrin was greater, though not significantly so, in patients with colon cancer before surgery (mean (SD) 17.4 (3.6) pmol/l, n = 16) compared with control subjects (12.6 (1.9) pmol/l, n = 14). Postprandial increases in serum gastrin were significantly and persistently higher than normal in the cancer patients. These increases were due to a subset of six patients with serum gastrin concentrations greater than the control mean + 2 SD at 20 and 40 minutes (62 pmol/l-146 pmol/l). Four of the six patients had intra-abdominal metastases. The extent of the increase may well correlate with that of the disease. Surgical resection of the tumour resulted in a fall in serum gastrin values and probably reflects the cause of the hypergastrinaemia. Hypergastrinaemia may, therefore, be an important aetiological factor in colon carcinogenesis.

Abdominal Neoplasms↗
PubMed1991

Brain injury and cognitive function in late-onset psychotic depression.

Fourteen patients who developed a psychotic depression after age 45 were compared with 72 non-psychiatrically ill elderly control subjects using neuroimaging and neuropsychological (NP) tests. Despite the fact that the patients were not studied if they had an obvious dementia or neurological disease, structural brain abnormalities were found in approximately two-thirds of patients and in less than 10% of controls. The most common abnormality, subcortical white matter (WM) lesions, was thought to be vascular in etiology. Also, tumor and primary degenerative dementia were found more frequently in the patients. Compared to an age-, sex-, and education-matched control group, the patients performed more poorly on NP tests of frontal lobe, memory, and visual spatial abilities. Diagnostic evaluation of the patient with late-onset psychotic depression should include computed tomography or magnetic resonance imaging as structural brain abnormalities are common in these patients.

Age of Onset↗