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Biomedical subjects

Y L Ong

Publications and source records attributed to Y L Ong.

13 recordsLinked to original sources
PubMed2000

High bax expression is a good prognostic indicator in acute myeloid leukaemia.

Most cytotoxic drugs kill cells by instigating the process of apoptosis and it has been suggested that apoptotic markers may provide an indication of tumour chemosensitivity. The aim of this study was to determine if such a relationship exists in acute myeloid leukaemia (AML). The levels of spontaneous apoptosis, bcl-2 and bax were evaluated in 56 newly diagnosed AML patients to determine if they correlated with a response to cytotoxic therapy. Spontaneous apoptosis was lower, but bcl-2, bax and the bcl-2/bax ratio were higher in AML compared with normal individuals. AML patients with high bax expression at diagnosis had significantly better prognosis for disease-free survival, event-free survival and overall survival (P = 0.016). In the standard risk group, high bax expression was in keeping with significantly improved survival. Multivariate analysis revealed bax to be an independent predictor of survival. There was a significant reduction in bcl-2 and bax expression when AML patients entered complete remission and also in relapsed AML patients who entered a second remission. This study suggests that bax is a useful prognostic indicator in AML and may assist with therapeutic decision-making for patients in the standard risk category.

Acute Disease↗
PubMed1998

Molecular determinants of bacterial adhesion monitored by atomic force microscopy.

Bacterial adhesion and the subsequent formation of biofilm are major concerns in biotechnology and medicine. The initial step in bacterial adhesion is the interaction of cells with a surface, a process governed by long-range forces, primarily van der Waals and electrostatic interactions. The precise manner in which the force of interaction is affected by cell surface components and by the physiochemical properties of materials is not well understood. Here, we show that atomic force microscopy can be used to analyze the initial events in bacterial adhesion with unprecedented resolution. Interactions between the cantilever tip and confluent monolayers of isogenic strains of Escherichia coli mutants exhibiting subtle differences in cell surface composition were measured. It was shown that the adhesion force is affected by the length of core lipopolysaccharide molecules on the E. coli cell surface and by the production of the capsular polysaccharide, colanic acid. Furthermore, by modifying the atomic force microscope tip we developed a method for determining whether bacteria are attracted or repelled by virtually any biomaterial of interest. This information will be critical for the design of materials that are resistant to bacterial adhesion.

Bacterial Adhesion↗
PubMed1998

The octreotide suppression test and [111In-DTPA-D-Phe1]-octreotide scintigraphy in neuroendocrine tumours correlate with responsiveness to somatostatin analogue treatment.

OBJECTIVE: The somatostatin analogue octreotide (Sandostatin, Novartis, Basie) significantly improves the syndromes suffered by most patients with neuroendocrine tumours (NETs). The use of [111In-DTPA-D-Phe1]-octreotide scintigraphy ([111In]-pentetreotide) to predict the response to octreotide treatment has been described. Short-term hormone inhibition by a single injection of octreotide has also been reported. This study aimed to compare the effects of the suppression test with the response to long-term somatostatin analogue treatment, and to seek a correlation between the short-term suppression test, [11In]-pentetreotide observations and long-term somatostatin analogue treatment. DESIGN AND MEASUREMENTS: Short octreotide suppression test and octreotide scintigraphy. Blood samples were collected before (0900, 0930 h), at (1000 h), and after (1030, 1100, 1200, 1300 h) the injection of 50 micrograms octreotide subcutaneously. Plasma hormones relevant to the syndrome were analysed by radioimmunoassay. The short suppression effects, the [111In]-pentetreotide observations and the response to long-term treatment with somatostatin analogue were evaluated and compared. PATIENTS: Twenty-six patients with metastatic NETs were evaluated, including 14 carcinoid tumours, 10 pancreatic endocrine tumours and 2 medullary carcinomas of thyroid (MCTs). Twelve patients had received octreotide treatment before the study, another 4 patients were treated subsequently with somatostatin analogue. RESULTS: During the short suppression test, hormones relevant to the syndromes were suppressed in 24 patients (those with carcinoids and pancreatic endocrine tumours). There was no suppression in the 2 patients with MCT. [111In]-pentetreotide observations closely correlated with the short suppression response to octreotide. Fourteen patients were treated with somatostatin analogue, and responded clinically; they had a positive short inhibition test and positive tumour uptake. Two patients with MCT did not respond to the treatment and had a negative suppression test and a negative [111In]-pentetreotide. CONCLUSION: Our results suggest that a consistent relationship exists between the short suppression test and the response to somatostatin analogue treatment in the majority of the patients with neuroendocrine tumours. The octreotide suppression test and octreotide scintigraphy together will be helpful in selecting appropriate patients for clinical treatment with somatostatin analogues.

Adult↗
PubMed1998

Evaluating the interaction of bacteria with biomaterials using atomic force microscopy.

Bacterial infection of biomaterials represents one of the most important reasons for the failure of transdermal or implanted medical devices. The first and least understood step in biomaterial-associated infections is the initial interaction between bacteria and a surface. This initial interaction can be either attractive or repulsive depending on the physiochemical nature of the biological and synthetic surfaces, as well as the properties of the interstitial fluid. We have shown that atomic force microscopy (AFM) can be employed as an exquisitely sensitive and versatile tool for quantifying the interaction between bacteria and surfaces in physiological solutions. The forces of interaction between an AFM cantilever tip and a uniform lawn of bacteria immobilized on glass were determined. By comparing the interactions of cantilever tips with lawns of isogenic E. coli strains carrying genetic lesions that alter their cell surface composition, it was possible to evaluate the effect of macromolecules such as lipopolysaccharide and capsular polysaccharide on the adhesion process. Mutations that result in the synthesis of truncated lipopolysaccharide or in the overproduction of the negatively charged capsular polysaccharide colanic acid render the interaction of the bacteria with the AFM tip unfavorable due to increased electrostatic repulsion. Furthermore, AFM could be used to evaluate the adhesion of bacteria onto commercially relevant biomaterials. In one approach, micron-size polystyrene beads were attached to AFM tips which were then used to measure forces. Unfortunately, this approach is limited by the meager number of materials manufactured as beads of a size suitable for AFM measurements. As an alternative approach, AFM cantilever tips were coated with a confluent layer of bacteria and used to probe planar surfaces. In this configuration, AFM could be employed to measure the force of interaction between virtually any bacterium and surface of interest.

Bacterial Adhesion↗
PubMed1998

A cluster of suspected Pneumocystis carinii Pneumonia following intensive chemotherapy in a Belfast haematology unit.

Five cases of pneumocystis carinii pneumonia were diagnosed in adult patients following intensive chemotherapy in the Royal Group of Hospitals haematology unit, Belfast, within a space of six months. The common features and the risk factors contributing to the increased susceptibility of these patients are discussed, as are the likely mechanisms of transmission of infection.

Adrenal Cortex Hormones↗
PubMed1989

A profile of long-stay psychogeriatric patients.

An assessment of 106 long-stay psychogeriatric in-patients in an East London borough was made using the CAPE and supplementary items in order to obtain a comprehensive picture of their needs; 51 long-stay residents in the care of local authority social services provided a comparison. Patients in hospital were found to be more disturbed, more disabled and more dependent than residents in local authority care.

Activities of Daily Living↗
PubMed1984

Blood donor motivation in Singapore.

75 first time donors were interviewed in detail at their first presentation at the Singapore Blood Transfusion Service. In addition they were asked to complete forms which elicited the motivating factors behind donating blood as well as the Crown Crisp Experiential Index. The results of this study show that the main motivating factor in these donors was that of an altruistic and humanitarian desire to help people. A high proportion (2/3) had some previous personal or familial contacts with the blood service. It also reports these donors as being more social and emotional people. These findings correlate with other studies and have implications for setting up blood donor recruitment programmes.

Adult↗
PubMed1983

Lithium levels in white blood cells and their relationship to observed side effects.

A strong correlation was obtained between white blood cell (WBC) lithium concentrations and the severity of observed side effects in a group of 40 patients receiving prophylactic lithium therapy. However, there was no significant correlation between these levels and the specific side effect of hand tremor, although WBC concentrations were higher in patients with greater tremor. These results contrasted with those for plasma and red blood cell (RBC) lithium concentrations, which showed no relationship to side effects. This suggests that WBC lithium concentrations may be a more sensitive index of side effects than conventional plasma estimations.

Adult↗
PubMed1983

Suppression of bulimic symptoms with methylamphetamine.

Eight patients with bulimia nervosa were given methylamphetamine or placebo intravenously under double blind controlled conditions. In every patient, methylamphetamine reduced self-ratings of hunger and amount of food eaten as measured under laboratory conditions. This shows that the food intake of patients with bulimia nervosa can be modified by experimental drugs. The symptom of bulimia (rapid, excessive and distressing eating) which may be followed by self-induced vomiting or purgation was seen in four patients after receiving placebo but in none after receiving methylamphetamine. These findings suggest that the severe symptom of bulimia may be amenable to drug treatment. Further studies are needed to explore the mechanism by which methylamphetamine appears to prevent bulimia.

Adult↗