Search PubMed⌕ Search

Biomedical subjects

S Tong

Publications and source records attributed to S Tong.

At least 55 records · Page 3Linked to original sources
PubMed2000

Ambient sulfate concentration and chronic disease mortality in Beijing.

In this study, ecological analysis was used to assess the relationship between ambient air pollution and human mortality. All the data on environmental measures and related factors, population size and number of deaths were collected for the city of Beijing, PR China and its eight districts for the years 1980-1992. In this study the concentration of SO(4)2- was selected as a main indicator of environmental pollution for the following reasons: (i) SO(4)2- data are available to cover all urban and suburban areas in Beijing compared with other air pollutants during the study period; (ii) SO(4)2- levels indicate the concentration of sulfide (include sulfate) and acid fog in the air, and they are significantly lower in cleaner districts than in others; and (iii) analyses showed that SO(4)2- levels are significantly correlated with daily mean concentrations of sulfur dioxide and nitrogen oxide, annual coal combustion, number of households using gas fuel, counts of motor vehicles and population density. Age-standardised mortality rates due to specific diseases were calculated using the Chinese population census data in 1990. Statistically significant correlations were observed between SO(4)2- concentration and total mortality and mortality due to cardiovascular disease, malignant tumour and lung cancer (r > 0.50 in all cases). The correlations were not only found between the current SO(4)2- concentration and these mortalities, but also for SO(4)2- levels measured up to 12 years prior to death, which may suggest long-term effects of air pollution. No significant correlations were observed for mortality from respiratory diseases and cerebrovascular diseases (r = 0.30-0.50). This study indicates that the concentration of SO(4)2- in air is a useful air pollution indicator in the areas where coal is used as the main source of energy. Areas with high levels of SO(4)2- experienced higher mortality due to a variety of chronic diseases.

Air Pollutants↗
PubMed2000

Oligomerization, secretion, and biological function of an anchor-free parainfluenza virus type 2 (PI2) fusion protein.

A number of studies indicate that the transmembrane domain, the cytoplasmic domain, or both regions of viral surface glycoproteins are involved in quaternary structure formation. In this report, the transmembrane domain and cytoplasmic tail coding sequence of the fusion (F) glycoprotein gene from parainfluenza type 2 virus was truncated by PCR and the resulting gene (PI2F') was expressed in HeLa-T4 cells by using the vaccinia virus-T7 transient expression system. Pulse-chase experiments indicated that the anchor-free PI2F' was expressed and processed into F(1) and F(2) subunits. Both the processed and the unprocessed anchor-free PI2F' proteins were found to be efficiently secreted into the culture medium. Examination of the oligomeric form of the anchor-free PI2F' by chemical cross-linking demonstrated that it assembles posttranslationally into dimers and trimers with a pattern similar to that of the wild-type PI2F protein. In an effort to better understand the biological properties of the truncated form of PI2F', we anchored PI2F' by a glycosyl-phosphatidylinositol (GPI) linkage. The GPI-anchored PI2F' protein, when coexpressed with PI2HN, did not induce cell fusion seen as syncytium formation, but was found to initiate lipid mixing (hemifusion) as observed by transfer of R-18 rhodamine from red blood cells to the GPI-PI2F'/PI2HN cotransfected cells. The results therefore indicate that the extracellular domain of the PI2 fusion protein contains not only the structural information sufficient to direct assembly into higher oligomers, but also is competent to initiate membrane fusion, suggesting that the anchor-free PI2F' may be useful for further structural studies.

Mutation↗
PubMed2000

Comparison of Abbott LCx Chlamydia trachomatis assay with Gen-Probe PACE2 and culture.

In this study the LCx assay (a nucleic acid amplification assay) for Chlamydia trachomatis in endocervical samples was compared with the Gen-Probe PACE2 assay (a nucleic acid probe assay) for endocervical samples, and with endocervical culture. In addition, the efficacy of the LCx assay was determined for midstream clean-catch urine samples because it is often necessary to obtain such a sample for routine urine culture and it is simpler to collect only a single sample without also collecting a first-void urine for LCx. Endocervical specimens from 205 patients were tested for C. trachomatis via LCx and PACE2. Of these patients, 203 were tested by culture. Midstream clean-catch urine samples from 75 of these patients were tested by LCx. The sensitivities and specificities for these assays, after discrepant analysis, were 100 and 98.9% for LCx of endocervical samples, 52.4 and 100% for PACE2; and 71.4 and 100% for culture. The sensitivity/specificity of LCx for midstream clean-catch urines was 66.7/98.5%. The apparent prevalence of C. trachomatis in our population was 10.2%. These data indicate that among the methods tested, LCx of endocervical samples had the highest sensitivity for C. trachomatis in this population. The sensitivity of the urine LCx assay using midstream clean-catch collected urines was considerably less than that reported in other studies that used first-void urines but was higher than that of PACE2.

Adolescent↗
PubMed2000

Parity is a major determinant of success rate in medical abortion: a retrospective analysis of 3161 consecutive cases of early medical abortion treated with reduced doses of mifepristone and vaginal gemeprost.

The antiprogesterone mifepristone in combination with a suitable prostaglandin provides an effective method for induction of abortion in early pregnancy up to 63 days of gestation. The combination of 600 mg mifepristone followed by 1 mg of gemeprost vaginal pessary 48 h later is one of the standard regimens in practice, which is registered in several countries in Europe. In 1995, we reduced the doses for both mifepristone and gemeprost to 200 mg and 0.5 mg respectively, as this was shown to decrease significantly the incidence of side effects whilst maintaining a high efficacy. In this article, we report our experience with this regimen in routine clinical practice by analysing 3161 consecutive medical abortions retrospectively. Twelve case notes (0.4%) were not available, and for 310 (9.8%) women, the outcome was not known with certainty as they did not return for their follow up visit. Of the remaining 2839 women, 2732 (96.2%) had a complete abortion following their treatment. One-hundred-two (3.6%) women required an evacuation of the uterus: for incomplete abortion in 63 (2.2%) and ongoing pregnancy in 39 (1.4%). Three women had to undergo surgery for ectopic pregnancies. The surgical intervention rate was significantly higher at gestation of >49 days compared to < or = 49 days (5.7% vs. 2.6%, p = 0.002) and at >56 days than among those at < or = 56 days (6.7% vs. 3.1%; p <0.001). However, for incomplete abortion a significant increase was only seen at gestation >49 days compared to < or = 49 days (3% vs. 1.6%, p = 0.017). The incidence of ongoing pregnancies increased significantly only after 56 days of gestation compared to < or = 56 days (3.8% vs. 0.9%; p <0.001). Parity was related to the outcome with parous women having significantly more incomplete/ongoing abortions compared to nulliparous women (5.4% vs. 2.0%; p <0.001), although parous women did present earlier in pregnancy for termination than nulliparous women (p = 0.01). The incidence of complications was low: 165 (5.8%) women were given antibiotics for presumed genital infection and severe haemorrhage occurred in 11 (0.4%) women, of whom only two required blood transfusion. In summary, the recommended regimen with the reduced doses of mifepristone and gemeprost is highly effective, meeting the anticipated efficacy with a complete abortion rate of >95%. We have concluded from the data that gestation and parity are strong predictors for clinicians to anticipate the probability of a successful medical termination of pregnancy.

Abortifacient Agents, Nonsteroidal↗
PubMed2000

Family self-medication and antibiotics abuse for children and juveniles in a Chinese city.

To identify the determinants of self-medication and antibiotics abuse by parents treating their children aged between 2 and 18 over the previous year, an investigation was conducted in Hefei City, China in April, 1995. A total of 1596 students from a kindergarten, a primary school and a high school were included in the study, and 1459 completed questionnaires were collected (the response rate: 91.4%). The results showed the rate of parental self-medication for their children in the sample was 59.4%. It increased with children's age; about 51% of children had received parental self-medication on six or more occasions during the 1-year period and 32.8% on four to five occasions; there were associations between parental self-prescribers and sources of medicine and severity of disease. The rate of antibiotics abuse was 35.7%. Logistic regression analysis showed that there were significant associations between self-medication and payment of the mother's medical fees by employers, severity of diseases as well as the mother's educational level.

Adolescent↗
PubMed2000

Migration bias in ecologic studies.

Differential migration may provoke bias in an epidemiological assessment of the public health risks from exposure to environmental agents, particularly in ecologic studies of health outcomes with a long latency or induction period. The potential impact of migration bias on epidemiological research is complex, and it depends not only on the direction of the factor-related migration, but also on its extent. This study shows that even a small amount of differential migration can bias the assessment of the exposure outcome relationship. Migration bias may result from a number of circumstances that are related to the way in which 'populations' are defined and ascertained. It is important to understand and minimise this type of bias in epidemiological research.

Air Pollution↗
PubMed2000

Older patients in the acute care setting: rural and metropolitan nurses' knowledge, attitudes and practices.

Many studies reporting nurses' knowledge of and attitudes toward older patients in long-term care settings have used instruments designed for older people. However, nurses' attitudes toward older patients are not as positive as their attitudes toward older people. Few studies investigate acute care nurses' knowledge of and attitudes toward older patients. In order to address these shortcomings, a self-report questionnaire was developed to determine nurses' knowledge of, and attitudes and practices toward, older patients in both rural and metropolitan acute care settings. Rural nurses were more knowledgeable about older patients' activities during hospitalisation, the likelihood of them developing postoperative complications and the improbability of their reporting incontinence. Rural nurses also reported more positive practices regarding pain management and restraint usage. However, metropolitan nurses reported more positive attitudes toward sleeping medications, decision making, discharge planning and the benefits of acute gerontological units, and were more knowledgeable about older patients' bowel changes in the acute care setting.

Acute Disease↗
PubMed2000

Acute-care nurses' attitudes towards older patients: a literature review.

With increases in life expectancy and increasing numbers of older patients utilising the acute setting, attitudes of registered nurses caring for older people may affect the quality of care provided. This paper reviews recent research on positive and negative attitudes of acute-care nurses towards older people. Many negative attitudes reflect ageist streotypes and knowledge deficits that significantly influence registered nurses' practice and older patients' quality of care. In the acute setting, older patients experience reduced independence, limited decision-making opportunities, increased probability of developing complications, little consideration of their ageing-related needs, limited health education and social isolation. Available instruments to measure attitudes towards and knowledge about older people, although reliable and valid, are outdated, country-specific and do not include either a patient-focus or a caring perspective. This paper argues for the development and utilisation of a research instrument that includes both a patient focus and a caring dimension.

Aged↗
PubMed2000

Dynamic splitting of large intensity-modulated fields.

The aims of this paper are to describe a method of splitting large intensity-modulated fields that cannot be delivered as a single field and to verify the accuracy of our method. Some multi-leaf collimators may be operated in the dynamic mode to deliver intensity-modulated radiation treatments (IMRT) using the 'sliding window' technique. In this technique each pair of leaves sweeps over the treatment field while the beam is on. However, there are limitations on the width of the field that can be treated due to the limited length of the leaves. For instance, the leaf length of the Varian MLC is 14.5 cm. Since each leaf pair must travel from the left boundary to the right boundary of the beam aperture, the maximum width of the field aperture that can be accommodated in one sweep of leaves is also limited to 14.5 cm, in fact to a slightly smaller value. It has been shown that IMRT is more efficient when used to plan and deliver the large and boost fields simultaneously. In such situations, the fields must be large enough to cover simultaneously the volumes of the gross tumour, microscopic disease and electively treated regions. Such field sizes are often larger than 14.5 cm wide. In this paper, we present a dynamic 'feathering' technique to split the large intensity-modulated fields into smaller fields. In this technique, the component beams overlap each other by a small amount, and the intensity in the overlap region gradually decreases for one field component and increases for the other. The sum of intensities remains the same as for the original field. This method eliminates the field matching problems associated with the conventional step 'break' for static fields. The splitting process is integrated into the IMRT treatment procedure and the entire planning process is automated. Comparison of dose distributions calculated and measured in a phantom showed good agreement. Such a method can be applied to the 'step and shoot' technique as well. IMRT fields of widths up to 25 cm can be delivered by splitting only once, which is adequate for most treatments.

Algorithms↗
PubMed2000

An automated approach to seed assignment for eye plaque brachytherapy.

Episcleral plaques are commonly used for the treatment of ocular tumours such as choroidal melanoma. Treatment planning involves the assignment of seeds to slots on the plaque to achieve a desired dose rate distribution. Seed assignment is rather straightforward if seeds are ordered on demand. However, the assignment task becomes tedious and laborious if the seeds have to be chosen from an existing stock of seeds with different activities. To date, this task has usually been performed by a human planner through trial and error. An algorithm has been developed to automate the task of seed assignment using a mixed-integer programming method. We also explore ways to simplify the problem such that the method becomes practical in most facilities. We have tested the method on three randomly chosen clinical cases from our past records, to show that the algorithm could yield solutions within a shorter time frame and with less deviation from the desired dose rate distributions, as compared with the solutions from a human counterpart.

Algorithms↗
PubMed2000

The potential impact of global environmental change on population health.

Due to rapid industrial changes and increased pressure of people on fragile ecosystems, large-scale environmental perturbations have been occurring on Earth. Major current environmental problems that can be expected to have a substantial effect on human health include human-induced climate change and stratosphere ozone depletion, because they threaten the ecological support systems on which human life depends. The most serious potential consequence of global environmental change is the erosion of Earth's life-support systems. The public health assessments of the present and future anthropogenic damage to the biosphere have important implications for human health and wellbeing. Medical practitioners have an important role to play in this field.

Climate↗
PubMed2000

Socio-demographic correlates of screening intention for colorectal cancer.

OBJECTIVE: To assess the relationship between socio-demographic factors and screening intention for colorectal cancer (CRC). METHODS: A cross-sectional survey of a random sample of 884 Queenslanders aged 40-80 years was conducted using a computer-assisted telephone interviewing system. The factors measured included socio-demographic characteristics, personal history of CRC, knowledge of others with CRC and perceived symptom status. Chi-squared and Monte Carlo estimates of Fisher Exact Tests were performed to determine the associations between socio-demographic factors and screening intention. In multivariate analyses, multinomial logistic regression (MNLR) was utilised to examine potential determinants of screening intention. RESULTS: 77.5% (95% CI 74.0%-80.7%) of the respondents indicated their intention to participate in CRC screening if it were recommended by their doctor or health authorities. The likelihood ratio chi-squared tests in the MNLR analyses show that age (chi(df = 6)2 = 15.0; p = 0.02), education (chi(df = 8)2 = 19.4; p = 0.01), perceived symptom status (chi(df = 4)2 = 22.9; p = 0.00), sex (chi(df = 2)2 = 4.5; p = 0.11), income (chi(df = 14)2 = 19.6; p = 0.14) and personal history of CRC (chi(df = 2)2 = 4.3; p = 0.12) were potential determinants of screening intention. Other socio-demographic factors, including country of birth, private health insurance status, Socio-economic Index for Areas, and Rural and Remote Areas Classification codes, were not associated with screening intention. CONCLUSIONS AND IMPLICATIONS: The results indicate that a variety of socio-demographic factors are associated with screening intention and need to be considered in the future development of a population-based screening program for CRC.

Adult↗
PubMed2000

The impact of fluctuations in intensity patterns on the number of monitor units and the quality and accuracy of intensity modulated radiotherapy.

The purpose of this work is to examine the potential impact of the frequency and amplitude of fluctuations ("complexity") in intensity distributions on intensity-modulated radiotherapy (IMRT) dose distributions. The intensity-modulated beams are efficiently delivered using a multileaf collimator (MLC). Radiation may be delivered through a continuous (dynamic mode) or discrete (step-and-shoot) sequence of windows formed by the leaves. Algorithms and software that convert optimized intensity distributions into leaf trajectories apply approximate empirical corrections to account for the various effects associated with MLC characteristics, such as the rounded leaf tips, tongue-and-groove leaf design, leaf transmission, leaf scatter, and collimator scatter upstream from the MLC. Typically, the difference between inter- and intraleaf transmissions is ignored. In this paper, using a schematic example of IMRT for head and neck carcinomas, we demonstrate that complex anatomy and severe optimization constraints produce complex intensity patterns. Using idealized intensity patterns we also demonstrate that, for complex intensity patterns, the average window width tends to be smaller and, for the same dose received by the tumor, the number of MUs is larger. We found that as the complexity increases, so does the contribution of radiation transmitted through and scattered from the leaves ("indirect radiation") to the total delivered dose. As a consequence, the lowest deliverable intensity in complex intensity patterns may be significantly greater than that required to provide adequate protection for some normal tissues. Furthermore, since corrections for leaf transmission and scatter effects are approximate and the difference between inter- and intraleaf transmission is ignored, the accuracy of the delivered dose may be affected. Using the results of a simple experiment and a typical intensity-modulated beam for a head and neck case as examples, we show the effect of window width and complexity on the accuracy and deliverability of intensity patterns. Some possible strategies for improving the accuracy and for relaxing the lower limit on deliverable intensity are discussed.

Biophysical Phenomena↗
PubMed2000

Dizygotic to monozygotic twinning ratio at The Royal Women's Hospital, Melbourne 1947-1997, compared with Australian national twinning incidence.

The incidence of dizygotic (Dz) twinning can be used as an index of natural human fertility. A retrospective study was done at The Royal Women's Hospital, Australia, to see whether the dizygotic to monozygotic (Mz) twinning ratio from one hospital can accurately reflect the national incidence of Dz twinning. The yearly twinning incidence from 1947-1997 was expressed as a Dz:Mz ratio, standardised for maternal age and plotted against previously published national statistics. The proportion of mothers born in Asia (of both singleton and multiples) between 1983-1997 was analysed to see whether different racial mixes might influence twinning trends. There were 5275 twins born of known sex and maternal age between 1947-1997. The age-standardised Dz:Mz ratio increased non-significantly from 1.39 in 1947 to 2.29 in 1953 (P = 0.08), underwent a significant decline to 0.73 in 1977, then remained stable until 1997 (P>0.05). The same trends were also apparent when the data was pooled into 2-year groups with the increase from 1947/48-1953/54 becoming highly significant (P<0.009). These trends observed in the hospital-based data were in close agreement with those found in the national statistics, with the exception of a rise in 1977-1982 only reflected in the Australia-wide data. In 1993, 2.6% of mothers were born in Asian countries; by 1997, this had risen to 10.6%. We found that the Dz:Mz ratio from one hospital closely reflects national twinning trends. Prospective studies must account for race, and would need around 200-300 twin pairs per year to minimise fluctuations of the ratio.

Australia↗
PubMed2000

Environmental lead exposure: a public health problem of global dimensions.

Lead is the most abundant of the heavy metals in the Earth's crust. It has been used since prehistoric times, and has become widely distributed and mobilized in the environment. Exposure to and uptake of this non-essential element have consequently increased. Both occupational and environmental exposures to lead remain a serious problem in many developing and industrializing countries, as well as in some developed countries. In most developed countries, however, introduction of lead into the human environment has decreased in recent years, largely due to public health campaigns and a decline in its commercial usage, particularly in petrol. Acute lead poisoning has become rare in such countries, but chronic exposure to low levels of the metal is still a public health issue, especially among some minorities and socioeconomically disadvantaged groups. In developing countries, awareness of the public health impact of exposure to lead is growing but relatively few of these countries have introduced policies and regulations for significantly combating the problem. This article reviews the nature and importance of environmental exposure to lead in developing and developed countries, outlining past actions, and indicating requirements for future policy responses and interventions.

Adult↗
PubMed2000

[The summarization of clinical experience of difficult tracheal intubation].

OBJECTIVE: To summarize our experiences and lessons of difficult tracheal intubation for clinical anesthesia reference. METHODS: We had done a retrospective analysis of clinical data on difficult tracheal intubation in 2,825 patients undergoing elective plastic surgery with anesthesia. The main causes of difficult tracheal intubation were the limitations of neck extension (n = 1,169), mouth opening (n = 889), both neck extension and mouth opening (n = 698), and micromaxillary deformity (n = 69). By the Cormack's classification, all the patients had the laryngeal exposure of grade II or more. The tracheal intubations were done under neuroleptanalgesia combined with topical spray of local anesthetic in 439 patients, intravenous anesthesia of sedative drugs and nondepolarizing relaxants of subnormal doses in 629 subjects, and total intravenous or inhaled anesthesia in 1,757 cases, respectively. RESULTS: The difficult tracheal intubations were completed using blind nasal intubations in 142 patients, blind oral intubations with direct laryngoscope in 2,377 patients, oral intubations with fiberoptic stylet rigid laryngoscope in 186 patients, and oral or nasal intubations with flexible fiberoptic bronchoscope in 72 patients. The incidence of successful intubation was 99.7%. The common complication of intubation was airway trauma and its incidence was 19.3% in all the patients. Anesthetic techniques could affect significantly the intubation time and the incidences of complications in the patients with difficult intubation. CONCLUSIONS: By the improvement of anesthetic methods and common intubation techniques, the intubation time and the incidence of complications in the patients with difficult intubations were reduced.

Adolescent↗