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Biomedical subjects

G Ong

Publications and source records attributed to G Ong.

At least 19 recordsLinked to original sources
PubMed2006

Antimicrobial resistance in non-typhoidal salmonellas from humans in Northern Ireland, 2001-2003: standardization needed for better epidemiological monitoring.

This study investigated the identification and antimicrobial susceptibility testing of Salmonella isolates in Northern Ireland during 2001-2003. All six participating hospital laboratories used similar methods. Identification and antimicrobial resistance of human enteric (n=897) Salmonella isolates were analysed by retrospective collation of laboratory records. Resistance of human Salmonella isolates to nalidixic acid was 16% but resistance to ciprofloxacin or cefotaxime was rare (<1%). Minor inter-laboratory variations in sensitivity testing practices make it difficult to compare antimicrobial sensitivity results reliably and also to monitor for epidemic clones such as S. Typhimurium DT104 with the ACSSuT resistance pattern. The outcome of this study was the adoption of a standardized regional approach to the isolation of salmonella antimicrobial resistance. This should improve epidemiological monitoring of epidemic clones and assure optimum treatment options are available. In cases of treatment failure, MICs to third-generation cephalosporins and ciprofloxacin should be determined.

Anti-Infective Agents↗
PubMed2005

Changes in chromatic and achromatic contrast sensitivities following tropicamide administration.

PURPOSE: To investigate the effects of tropicamide on chromatic and achromatic contrast sensitivities over the physiological range of spatial frequencies. METHODS: A total of 26 healthy volunteers, with a mean age of 32 years, were examined with and without one drop of 1% tropicamide being administered 30 min previously. On each occasion, acuity and pupil diameter were recorded, and chromatic and achromatic contrast sensitivities were examined using the Sussex Grating Machine. RESULTS: Following tropicamide administration mean pupil diameter increased from 4.1 mm to 7.2 mm (P<0.001), and mean BCVA was reduced by 0.07 LogMar units (P<0.001). Achromatic contrast sensitivity was significantly reduced following tropicamide administration at 2.20 cycles per degree (cpd) (P=0.01), 3.40 cpd (P=0.01), 10 cpd (P=0.04), 17 cpd (P=0.04), and 25 cpd (P<0.01). There was no difference in contrast sensitivity at lower spatial frequencies (0.33 and 0.66 cpd). Chromatic contrast sensitivity was not significantly altered when tested along the red-green and tritan confusion axes. CONCLUSIONS: Achromatic contrast sensitivity is significantly reduced following tropicamide administration at intermediate and high spatial frequencies. No significant changes were seen at low spatial frequencies and in chromatic contrast sensitivities.

Administration, Topical↗
PubMed2005

Inhibition of TNF-alpha improves indomethacin-induced enteropathy in rats by modulating iNOS expression.

TNF-alpha, including other proinflammatory cytokines alone or in combination, induces iNOS expression and upregulates inflammatory responses. We evaluated the relationship between TNF-alpha and iNOS expression in indomethacin-induced jejunoileitis in male Sprague-Dawley rats. Rats were fed a daily dose of a phosphodiesterase inhibitor-either theophylline or pentoxifylline-for 2 days. Jejunoileitis was induced with two subcutaneous injections of indomethacin (7.5 mg/kg) 24 hr apart and theophylline or pentoxifylline continued for 12 hr or 4 days. Other rats received a single intraperitoneal injection of anti-TNF-alpha monoclonal antibody (TNF-Ab) 30-min before indomethacin. At 4 days TNF-Ab, theophylline, or pentoxifylline treatment significantly decreased indomethacin-induced ulceration, myeloperoxidase activity, and disease activity index. Although indomethacin significantly increased serum TNF-alpha and nitrate/nitrite levels over the control value as early as 12 hr, iNOS expression was detected only after 4 days. Serum IL-1beta level did not change at 12 hr but increased fourfold at 4 days. Treatment with TNF-Ab, theophylline, or pentoxifylline significantly reduced serum/tissue TNF-alpha, IL-1beta, nitrate/nitrite, and iNOS expression. The downregulation of nitrate/nitrite by these inhibitors suggests that TNF-alpha modulates iNOS expression.

Animals↗
PubMed2001

Prevalence of Actinobacillus actinomycetemcomitans in an ethnic adult Chinese population.

AIM: The aim of this study was to determine the prevalence and the structure of the leukotoxin promoter region of Actinobacillus actinomycetemcomitans in an ethnic Chinese population. METHOD: Subgingival plaque samples were collected from 42 patients with moderate to advanced periodontitis and 50 periodontally healthy patients. A. actinomycetemcomitans was detected directly from the crude subgingival plaque by PCR using leukotoxin gene specific primers. The presence of A. actinomycetemcomitans was determined by a single 285 bp PCR amplicon. RESULTS: A. actinomycetemcomitans was found to be present in the subgingival plaque of 68 out of a total of 92 patients examined (74%). 29 out of the 42 periodontitis patients tested were carriers of A. actinomycetemcomitans (69%). Among the periodontally healthy patients studied, 39 out of 50 subjects possessed the bacteria (78%). PCR analysis of the promoter region of the ltx operon revealed that none of the 42 moderate to advanced periodontitis patients examined harboured A. actinomycetemcomitans strains with the JP2-like promoter of the ltx operon, known to enhance leukotoxin expression. 2 out of the 27 advanced periodontitis patients clinically diagnosed as suffering from rapidly progressive periodontitis were found to be carriers of the mildly toxic strain of A. actinomycetemcomitans with the characteristic 652-like promoter. CONCLUSIONS: The high prevalence of A. actinomycetemcomitans, regardless of whether the subgingival samples were analysed from patients with healthy or diseased periodontium suggests that this bacterial species is part of the normal oral flora of ethnic Chinese. Our preliminary results also suggested that subjects who harboured the mildly toxic strain of A. actinomycetemcomitans were potentially susceptible to aggressive forms of periodontitis.

Actinobacillus Infections↗
PubMed2001

Bacteroides forsythus prtH genotype in periodontitis patients: occurrence and association with periodontal disease.

Bacteroides forsythus has been described as a periodontopathogen and its presence in the subgingival plaque can lead to periodontal disease. Recently, a cysteine protease designated as prtH was isolated and characterized from B. forsythus ATCC 43037. The purpose of this study was to determine the prevalence and the association of the prtH gene of B. forsythus with periodontal disease. A total of 160 subgingival plaque samples were assayed with the polymerase chain reaction method using oligonucleotide primers targeting the prtH and the 16S rDNA genes of B. forsythus. Primers targeting the 16S rDNA gene of B. forsythus were used to determine the occurrence of the bacteria in the subgingival plaque samples at baseline. At baseline, B. forsythus was detected in 78 out of 86 (91%) diseased sites and 33 out of 74 (45%) healthy sites studied. Among the 86 diseased sites examined, 73 sites (85%) were colonized by the bacteria with the prtH genotype. In sites of the periodontally healthy, 7 out of 73 (10%) possessed B. forsythus with the prtH genotype. The results obtained suggested strong association of the prtH gene of B. forsythus with adult periodontitis. Although this bacterial species was detected from about half of the periodontally healthy samples, only a fraction of these subjects possess the bacteria strain with the prtH genetic subtype. We propose the use of the prtH gene as an alternative to the more widely used 16S rDNA gene of B. forsythus, for a more accurate determination of the prevalence of periodontal health and disease in epidemiological studies and clinical screening.

Adult↗
PubMed2001

Synthetic hybrid grafts for craniofacial reconstruction: sustained gene delivery using a calcium phosphate bone mineral substitute.

These experiments were performed to evaluate the efficacy of a biocompatible bone cement, Norian CRS, engineered as a hybrid graft for simultaneous bone matrix reconstruction and sustained, site-directed gene transfer using an adenoviral vector. Norian CRS was cured ex vivo by mixing a calcium source powder with a phosphate source solution to form a paste. To 1.0 ml of the cement was added 50 microl of a solution containing 1 x 10(8) plaque-forming units of a replication-deficient adenoviral vector containing a bacterial beta-galactosidase reporter gene (AdLacZ). In vitro, fragments of the hybrid Norian-AdLacZ construct were placed into 12-microm-pore culture plate inserts and cocultured with human fibroblasts. The same insert was transferred to a new well of fibroblasts every 48 hours for 30 days, and, after allowing 72 hours for gene expression, fibroblasts were examined for transgene expression by 5 bromo-4-chloro-3-indoyl-beta-D-galactosidase (X-gal) staining. In vivo, the Norian-AdLacZ hybrid was implanted into 10-mm frontal bone defects in 3-week-old piglets. The implant sites were harvested after 5 days and were examined for transgene expression by X-gal staining. X-gal staining of fibroblasts incubated with the hybrid Norian-AdLacZ construct was observed throughout the 30-day period. Transgene expression was also observed about the periphery of the calvarial defects treated with hybrid Norian-AdLacZ constructs. Thus, adenoviral vectors may be incorporated successfully into a synthetic calcium phosphate bone mineral substitute to provide effective, sustained local gene delivery.

Adenoviridae↗
PubMed2001

Toward an understanding of nonsyndromic craniosynostosis: altered patterns of TGF-beta receptor and FGF receptor expression induced by intrauterine head constraint.

Although the etiology of nonsyndromic forms of craniosynostosis remains uncertain, recent experiments from our laboratory have demonstrated that fetal head constraint induces cranial suture fusion in mice through a process associated with altered patterns of transforming growth factor beta (TGF-beta) isoform expression. Other recent studies have highlighted the role of secreted signaling molecules, including members of the TGF-beta superfamily and the fibroblast growth factors (FGFs), as well as their receptors, in regulating suture development and fusion. The purpose of these experiments was to examine the potential role of TGF-beta receptors and FGF receptor 2 (FGFR2) in nonsyndromic craniosynostosis by determining their temporospatial patterns of expression during development complicated by intrauterine head constraint. This study consisted of two groups of C57BI/6J mice: an experimental group subjected to intrauterine constraint and a control unconstrained group. Fetal head constraint was induced by performing uterine cerclage on day 17.5 of gestation and allowing intrauterine fetal growth to continue 24 and 48 hours beyond the normal gestational period. Control animals underwent hysterotomy on day 17.5 and the nonconstrained pups were allowed to continue intra-abdominal fetal growth 48 hours beyond normal gestation. Expression of TGF-beta receptor types I and II, and FGFR2 in the calvarial tissue was determined by immunohistochemical analysis. In the unconstrained control animals, there was minimal immunoreactivity for both TGF-beta receptors and FGFR2 within the coronal suture. After 24 hours of constraint, however, there was a marked increase in immunoreactivity of TGF-beta receptors and FGFR2 in the osteoblasts along the osteogenic fronts and in the dural cells. After 48 hours, there was continued expression of both type I and type II receptors and FGFR2 within the midsutural mesenchyme of the coronal suture, in the osteoblasts, and in the dura. The authors demonstrated substantial upregulation of TGF-beta receptor types I and II and FGFR2 in coronal sutures subjected to in utero constraint. These results suggest an important role for TGF-beta/TGF-beta receptor, and FGF/FGFR signaling in the pathogenesis of constraint-induced craniosynostosis.

Animals↗
PubMed1999

A comparison of the induction and emergence characteristics of sevoflurane and halothane in children.

This open labelled, randomised, controlled study was designed to compare the induction and recovery characteristics of sevoflurane and halothane anaesthesia in children. Forty American Society of Anaesthesiologist (ASA) physical status class 1 or 2 children (aged 1-10 year, weighed less than 25 kg) scheduled for elective urological procedure lasting less than one hour were allocated randomly to receive either sevoflurane (group S, n = 20) or halothane (group H, n = 20). The induction time in children receiving sevoflurane was significantly shorter than in those receiving halothane (mean (SD) 46 (13.6) second vs 69 (19.4) seconds, p < 0.005). The emergence from anaesthesia was also faster in children receiving sevoflurane than in those receiving halothane (mean (SD) 9 min (4.3 min) vs 21 min (8.9 min), p < 0.001). No major adverse effects were encountered in each group. We concluded that sevoflurane is comparable to halothane in Malaysian children.

Anesthesia, General↗
PubMed1998

Do women who undergo further investigation for breast screening suffer adverse psychological consequences? A multi-centre follow-up study comparing different breast screening result groups five months after their last breast screening appointment.

BACKGROUND: In 1995-1996 about 53500 women aged 50-64 attending for routine breast screening were called back for further investigation after an initial mammogram. Even when women were found to be clear after further investigation, significant adverse psychological consequences (PCs) can remain one month later. This follow-up study investigates whether residual emotional effects persisted five months after women received a clear result. METHODS: Women who had previously completed a questionnaire one month after their last breast screening appointment, at which they had a clear result, were invited to complete a further postal questionnaire four months later (five months after their last appointment). We compare women who received a clear result after assessment without fine needle aspiration cytology (FNAC), after assessment with FNAC, after a benign biopsy, and those who had been placed on early recall, with those who received a clear result after mammography (reference group). RESULTS: The response rate was 76 per cent (215/284). All groups of women who went on for further investigation suffered significantly greater adverse psychological consequences (PCs) at five months than women who were given a clear result after mammography. Compared with 10 per cent (5/52) of women who received a clear result after a basic mammogram, adverse psychological consequences were experienced by 59 per cent (27/46, p<0.00001) of the women who were placed on six month early recall, 61 per cent (14/23, p<0.0001) of women who had benign surgical biopsy, 44 per cent (18/41, p<0.0001) of women who received a clear result after assessment (with FNAC), and 45 per cent (23/51, p<0.0001) of women who received a clear result after assessment (without FNAC). Whereas all groups who had gone on for further investigations had experienced a significant decrease in PCs between one month and five months, those who were placed on six month early recall showed no significant difference in PCs between these two time periods. Other factors relating to adverse experiences as a result of breast screening are reported. CONCLUSION: Despite receiving a clear final result, women who undergo further investigation suffer significantly greater adverse psychological consequences five months after their last screening appointment than women who receive a clear result after mammography.

Adaptation, Psychological↗
PubMed1998

Out-of-hospital spinal immobilization: its effect on neurologic injury.

OBJECTIVE: To examine the effect of emergency immobilization on neurologic outcome of patients who have blunt traumatic spinal injuries. METHODS: A 5-year retrospective chart review was carried out at 2 university hospitals. All patients with acute blunt traumatic spinal or spinal cord injuries transported directly from the injury site to the hospital were entered. None of the 120 patients seen at the University of Malaya had spinal immobilization during transport, whereas all 334 patients seen at the University of New Mexico did. The 2 hospitals were comparable in physician training and clinical resources. Neurologic injuries were assigned to 2 categories, disabling or not disabling, by 2 physicians acting independently and blinded to the hospital of origin. Data were analyzed using multivariate logistic regression, with hospital location, patient age, gender, anatomic level of injury, and injury mechanism serving as explanatory variables. RESULTS: There was less neurologic disability in the unimmobilized Malaysian patients (OR 2.03; 95% CI 1.03-3.99; p = 0.04). This corresponds to a <2% chance that immobilization has any beneficial effect. Results were similar when the analysis was limited to patients with cervical injuries (OR 1.52; 95% CI 0.64-3.62; p = 0.34). CONCLUSION: Out-of-hospital immobilization has little or no effect on neurologic outcome in patients with blunt spinal injuries.

Adult↗
PubMed1998

Periodontal disease and tooth loss.

Numerous epidemiological studies have shown that caries is the main reason for tooth loss. More recent epidemiological data seem to show an increasing trend of tooth loss due to periodontal reasons rather than caries. In considering the issue of periodontal disease and tooth loss the following observations were made. The presence of initial attachment loss, bone height and the habit of smoking significantly increase the risk of tooth mortality. There is a strong correlation between smoking, the severity of periodontal disease and tooth mortality. Cross-sectional population surveys of tooth loss reported lower anterior teeth to be the most frequently extracted due to periodontal reasons, followed by upper anteriors and upper second molars. However, in long term maintenance studies, molars were lost most frequently. Periodontal reasons for tooth loss were mainly mobility followed by furcation involvement. Periodontal surgery did not significantly enhance tooth retention in high risk groups. Ethnic differences observed were not significant and would need further investigations to address variables such as cultural differences, health habits, diet and socio-economic status. In conclusion, periodontal tooth mortality was found to be associated with the loss of periodontal attachment and risk groups with advanced periodontitis contributing to major tooth loss in a minority of the population.

Alveolar Bone Loss↗
PubMed1998

Chlamydia pneumoniae in atheroma: consideration of criteria for causality.

AIMS: (1) To seek evidence of the existence of Chlamydia pneumoniae in a spectrum of atheromatous lesions in different types of arteries from individuals of different ages, using a polymerase chain reaction (PCR) assay supported by electron microscopy and immunocytochemistry; (2) to use electron microscopy to examine interactions between C pneumoniae and the cells present in the arterial tissue; (3) to assess the extent to which the data fulfil the criteria for causality. METHODS: At necropsy examination, 35 arterial specimens were taken from 25 subjects. The grade of atheroma was determined macroscopically and microscopically and the tissues coded and examined by the three techniques. RESULTS: Of the 35 specimens, 24 had macroscopic or microscopic atheromatous lesions of varying degree. Twenty two of the 35 specimens were examined by electron microscopy, C pneumoniae-like bodies being found in 11 (50%); seven specimens were examined by the immunocytochemical method, positive staining being detected in three; and all specimens were examined by the PCR technique, 15 (43%) being PCR positive. Overall, of the 24 specimens with lesions, 17 (71%) were positive by at least one of the three tests, whereas of the 11 specimens without lesions, only one was positive. The positive specimens comprised 10 of 19 aortas, three of six iliac arteries, and one coronary and one pulmonary artery. C pneumoniae was detected in four of six specimens in which there were early changes and in a 20 year old subject. Concerning the 25 subjects, of 17 who had atheromatous arteries, 14 (82%) were C pneumoniae positive and of the eight who had normal arteries, none was positive. CONCLUSIONS: There is a strong correlation between C pneumoniae and arterial atheromatous lesions. The organism may contribute to the disease process by damaging smooth muscle cells.

Adult↗
PubMed1997

Recalling women for further investigation of breast screening: women's experiences at the clinic and afterwards.

BACKGROUND: In 1993-1994 about 66 000 women in breast screening were called back (recalled) to a specialized centre for further investigation (assessment). The information requirements of these women during and after their appointment were investigated. Ninety per cent of recalled women were found not to have cancer. METHODS: Consecutive women (n = 2132) from eight breast screening centres throughout the United Kingdom were asked to complete a postal questionnaire two weeks after attendance at assessment. No reminder was sent. RESULTS: The response rate was 70 per cent. Communication was viewed by women as the most stress-relieving aspect of the recall appointment. Women from centres where nurses provided the opportunity to talk in private before further investigation were less likely to want to talk later about why assessment was needed for them (4 per cent) than women from centres not using a nurse for this purpose (30 per cent) (p < 0.0001). The former were also less likely to want more information about the tests they had had (2 per cent physical examination, 2 per cent X-rays, 3 per cent ultrasound) than the latter (6 per cent, 9 per cent and 10 per cent, respectively) (p < 0.005). Distressed/very distressed women were more likely to have wanted to talk to someone at the centre about the reason for recall (26 per cent) than somewhat distressed/ not distressed women (18 per cent) (p < 0.0001). However, the former were no more likely to have spoken to staff about it than the latter (33 per cent vs 32 per cent). Ways to improve the giving of results were identified. After the appointment women commented that there was a need for more information about harmless breast conditions. CONCLUSIONS: Overall the quality of communication at assessment was viewed highly by women, but varied considerably between centres. There is scope for substantial further improvement. Breast care nurses can play an important role in this.

Attitude to Health↗
PubMed1997

Breast screening: adverse psychological consequences one month after placing women on early recall because of a diagnostic uncertainty. A multicentre study.

BACKGROUND: It was the original intention of the UK National Health Service Breast Screening Programme (NHSBSP) to place women who were not diagnosed with cancer on three yearly routine recall (RR). In 1994-5 approximately 16,500 women, aged 50 to 64, were placed on early recall (ER) at a shorter time interval, of which about 98% will have a normal result. This large number exceeds the expectations of the NHSBSP. OBJECTIVE: To establish the adverse psychological consequences (PCs) for women one month after placement on ER because of a diagnostic uncertainty, and if detected, to suggest practical solutions to reduce them. METHODS: Thirteen breast screening centres throughout the UK participated in the study. From March to October 1995 all women who were placed on ER because of a diagnostic uncertainty were identified and compared with groups of women placed on RR (after mammography, assessment, fine needle aspiration, and a benign biopsy). These women were invited to complete a postal questionnaire one month after they were placed on ER or RR. One reminder was sent. RESULTS: Overall 75% of women completed the questionnaire. The adverse PCs of placing women on ER because of a diagnostic uncertainty were higher (63%; n = 81 of 130) than those of women placed on RR after mammography (29%; n = 38 of 130) (P < 0.00001) or assessment (50%; n = 64 of 128) (P < 0.05), but lower than the adverse PCs of women who underwent a benign biopsy (87%; n = 26 of 30) (P < 0.05). Factors that were significantly associated with subsequent adverse PCs were identified. CONCLUSIONS: The adverse PCs of being placed on ER because of a diagnostic uncertainty were significantly higher than those of women who turned out to have a false-positive mammographic result after assessment. Possible practical solutions are discussed.

Breast Neoplasms↗
PubMed1997

Endotracheal tube ignition during CO2 laser surgery of the larynx.

We report a case of endotracheal tube fire occurring during CO2 laser surgery of the larynx. The ignition of an endotracheal tube was thought to be caused by laser penetration of an unprotected portion of the tube during resection of vocal cord tumour. Fire hazard is inevitable when a laser is used in the path of combustible gases and in the presence of flammable objects. We discuss the methods of prevention that were used.

Aged↗