Biomedical subjects

M R Phillips

Publications and source records attributed to M R Phillips.

At least 19 recordsLinked to original sources

PubMed2006

Transient analysis of gaseous electron-ion recombination in the environmental scanning electron microscope.

Most of the work carried out in relation to contrast mechanisms and signal formation in an environmental scanning electron microscope has yet to consider the time dependent aspects of image generation at a quantitative level. This paper quantitatively describes gaseous electron-ion recombination (also known as 'signal scavenging') in an environmental scanning electron microscope at a transient level by utilizing the dark shadows/streaks seen in gaseous secondary electron detector images of alumina (Al2O3) immediately after a region of enhanced secondary electron emission is encountered by a scanning electron beam. The investigation firstly derives a theoretical model of gaseous electron-ion recombination that takes into consideration transients caused by the time constant of the gaseous secondary electron detector electronics and external circuitry used to generate images. Experimental data of pixel intensity versus time of the streaks are then simulated using the model enabling the relative magnitudes of (i) ionization and recombination rates, (ii) recombination coefficients and (iii) electron drift velocities, as well as absolute values of the total time constant of the gaseous secondary electron detection system and external circuitry, to be determined as a function of microscope operating parameters such as gaseous secondary electron detector bias, sample-electrode separation, imaging gas pressure, and scan speed. The results revealed, for the first time, the exact dependence that the effects of secondary electron-ion recombination on signal formation has on reduced electric field and time in an environmental scanning electron microscope. Furthermore, the model implicitly demonstrated that signal loss as a consequence of field retardation due to ion space charges, although obviously present, is not the foremost phenomenon causing streaking in images, as previously thought.

Journal Article↗

PubMed2002

Domestic exposure to formaldehyde significantly increases the risk of asthma in young children.

Concern has arisen in recent years about indoor air pollution as a risk factor for asthma. Formaldehyde exposure was examined in relation to asthma among young children (between 6 months and 3 yrs old) in a population-based control study carried out in Perth, Western Australia, between 1997-1999. An association between exposure to formaldehyde and asthma in young children has been suggested. Cases (n=88), whose parents were recruited at Princess Margaret Hospital Accident and Emergency Dept (Perth, Western Australia), were children discharged with asthma as the primary diagnosis. Controls (n=104), who were children in the same age group without asthma diagnosed by a doctor, were identified from birth records through the Health Dept of Western Australia (Perth, Western Australia). Health outcomes for the children were studied using a respiratory questionnaire and skin-prick tests. Formaldehyde, average temperature and relative humidity were measured on two occasions, winter (July-September 1998) and summer (December 1998-March 1999) in the child's bedroom and in the living room. The study found seasonal differences in formaldehyde levels in the children's bedrooms and living rooms with significantly greater formaldehyde exposure during the summer period for case and control subjects. The generalised estimating equation model showed that children exposed to formaldehyde levels of > or = 60 microg x m(-3) are at increased risk of having asthma. The results suggest that domestic exposure to formaldehyde increases the risk of childhood asthma.

Age Factors↗

PubMed2001

Estimation of postmortem interval. Temperature-correction of extracellular abdominal impedance during the first 21 days of death.

Extracellular impedance of the intact abdomen of rats increased from 79.0+/-7.4Omega, 1h postmortem (i.e. 0.04 day), to 130.5+/-14.4Omega at postmortem interval (PMI)=1 day. Impedance then decreased with time, reaching 64.2+/-9.9Omega at PMI=21 days. The time taken for mean abdominal impedance to decrease below the value at PMI=0.04 day averaged 16 days. It is therefore impossible, using extracellular abdominal impedance alone, to distinguish (in terms of interpolating PMI) between numerically equal impedances on the rising and falling phases of curves depicting impedance as a function of PMI. Correction of measured impedances to their theoretically-predicted values at an arbitrarily chosen temperature of 40 degrees C appreciably diminished the magnitude of the increase in impedance following death. Thus, temperature-corrected abdominal impedance increased from 56.2+/-4.8Omega at PMI=0.04 day to 59.5+/-6.2Omega at PMI=1 day. Impedance then decreased, reaching 29.2+/-4.1Omega at PMI=21 days. The time taken for mean, temperature-corrected abdominal impedance to decrease below the value at PMI=0.04 day averaged 3 days (as opposed to 16 days (see above) in the absence of temperature-correction). These findings are believed to improve the usefulness of extracellular abdominal impedance as a potential tool for estimation of postmortem interval.

Abdomen↗

PubMed2000

Repair of anterior leaflet mitral valve prolapse: chordal replacement versus chordal shortening.

BACKGROUND: To determine the optimal method of repair for severe, segmental anterior leaflet prolapse, we analyzed outcome of 121 patients who underwent chordal shortening (n = 46) and chordal replacement (n = 75) from 1988 to 1996. METHODS: Chordae were replaced with expanded polytetrafluoroethylene sutures. Patients had an annuloplasty with either chordal replacement or shortening. Follow-up was 100% complete (mean, 3.7 years). RESULTS: Mean age was 62.1 years, 86 were men, and 60 patients had isolated valve repair. There was one hospital death and 14 late deaths for a 5-year actuarial survival of 86.4%+/-4.5%. Sixteen patients underwent reoperation, 5 in the replacement group and 11 in the shortening group. Mechanism of valve failure in the replacement group was native chordae rupture (n = 4) and neochordae dehiscence (n = 1). With chordal shortening, repair failure was attributed to rupture of shortened chordae (n = 8), leaflet prolapse with and without annuloplasty ring dehiscence (n = 2), and native chordae elongation (n = 1). Risk of reoperation because of repair failure at 3.5 years was 1.4% in the chordal replacement group and 14.8% in the chordal shortening group (p = 0.02). CONCLUSIONS: Chordal replacement is superior to chordal shortening, providing a predictable method for correction of mitral regurgitation with a low incidence of reoperation.

Actuarial Analysis↗

PubMed2000

Development and validation of a calcium intake questionnaire for postmenopausal women in China.

PURPOSE: Develop and evaluate a food frequency questionnaire (FFQ) for assessing calcium intake in Chinese postmenopausal women. METHODS: An interviewer-conducted FFQ that asks respondents about their consumption of 110 calcium-containing foods over the previous week was developed and administered to 21 randomly selected postmenopausal women from Chengdu. This FFQ uses both the traditional weight-estimation method of assessing portion size in China and a new volume-estimation method. Test-retest reliability was assessed by re-administering the questionnaire two weeks later and validity was assessed by comparing the computed daily calcium intake to that obtained by a researcher-conducted 4-day food record. RESULTS: Estimates of calcium intake derived from the volume-estimation method were significantly lower than estimates derived from the traditional weight-estimation method (median calcium intakes = 270 mg/day versus 570 mg/day), but were quite similar to those obtained from the 4-day food record (median calcium intake = 275 mg/day). The test-retest reliability and validity of the volume-estimation method (intraclass correlation coefficient (ICC) = 0.73 and 0.86, respectively) were better than those of the weight-estimation method (ICC = 0.58 and 0.39, respectively). CONCLUSIONS: The reliability and validity of the traditional weight-estimation FFQ method of assessing dietary intake of nutrients in China is poor; this method may significantly overestimate dietary intakes. The proposed volume-estimation FFQ method for assessing calcium intake is a simple, interviewer-conducted method that is both reliable and valid. The calcium intake of postmenopausal women in urban China is much lower than the recommended daily allowance of 800 mg.

Aged↗

PubMed2000

Effects of transdermal nicotine treatment on structure and function of coronary artery bypass grafts.

Smoking is a major risk factor for failure of coronary artery bypass grafts (CABG). Experiments were designed to determine effects of transdermal nicotine, independent of smoking, on structure and function of CABG. Saphenous veins were placed as CABG in untreated dogs (control) or in dogs treated with transdermal nicotine (one 11-mg or two 22-mg patches/day) for 5 wk. Serum nicotine and plasma nitric oxide were measured. Grafts were removed and prepared for organ chamber studies and histology. Serum nicotine averaged 12.1 and 118.7 ng/ml in the 11 mg/day and 44 mg/day groups, respectively. Plasma nitric oxide was higher in dogs treated with 11 mg/day doses compared with controls. In organ chamber studies, endothelium-dependent relaxations to thrombin and A-23187 and endothelium-independent relaxations to nitric oxide were greatest in grafts from dogs treated with 11 mg/day doses. Intimal thickness of the grafts were similar among groups. However, staining for bone sialoprotein was increased in the media of grafts from the 11 mg/day treatment group. These data suggest that transdermal nicotine in doses comparable and double to those used for conventional smoking cessation treatment in humans does not adversely affect early patency of canine CABG up to 4 wk postoperatively. Transdermal nicotine, however, may increase production of and response to nitric oxide in bypass grafts.

Actins↗

PubMed2000

Causes of schizophrenia reported by patients' family members in China.

BACKGROUND: Better methods of assessing patients' and family members' causal models of illness are needed to improve adherence with biomedical interventions and to design services that meet the needs of consumers. AIMS: To develop a quantitative measure suitable for assessing the relationship of causal beliefs to expressed emotion, stigma, care-seeking and adherence. METHOD: The Causal Models Questionnaire for Schizophrenia, which includes 45 causes identified during in-depth interviews with family members, was administered to 245 family members of 135 patients with DSM-III-R schizophrenia in Suzhou and Siping, China at the time of admission to hospital. RESULTS: Respondents, who identified a mean of 2.5 causes (range 1-10, mode 2), attributed 84% of the cause of schizophrenia to social, interpersonal and psychological problems. Hence, their beliefs do not concur with Chinese professionals' ideas about the biomedical causes of schizophrenia. Multivariate analyses identified the socio-economic factors that influence family members' causal beliefs. CONCLUSIONS: Despite the complexity of causal models, measures can be developed that will help improve clinicians' communication with patients and understanding of help-seeking behaviours.

Adolescent↗

PubMed1999

Suicide and social change in China.

Using recently available data from China's Disease Surveillance Points system, we estimate that there are over 300,000 suicides in China per year; this makes suicide one of the most important causes of death in the country and makes the suicide rate in China one of the highest in the world. Moreover, the pattern of suicides in China is quite different than in other parts of the world--there are more completed suicides among females than males and rural rates are three-fold urban rates. The lack of reliable suicide data prior to 1987 makes it difficult to determine whether the rates are currently rising, falling, or staying constant. However, reports of suicides in the Chinese press and case studies conducted by the authors suggest (but do not prove) that the high rates of suicide currently experienced are related to the social changes that have occurred with the economic reforms (which started in 1978). Another possible explanation for the high rates of suicide is the large numbers of persons with depressive illness in China who remain untreated. Single-cause models of suicide (i.e., social factors or mental illness) do not do justice to the complexity of the processes involved and, therefore, do not provide useful information about the etiology and prevention of suicide in China or elsewhere. We describe our own dynamic model of suicide that includes five interacting factors which, we believe, collectively determine the suicide rates in a community.

Adolescent↗

PubMed1999

Randomised trial of different rates of feeding in acute diarrhoea.

OBJECTIVE: To compare the effect of different feeding frequencies on the speed of recovery from diarrhoea. METHODS: A randomised, non-blinded trial provided 0.452 MJ/kg/day as either 6 or 12 feeds of cows' milk each day to 262 hospitalised male infants aged 3-12 months with acute diarrhoea. Stool frequency, stool weight, body weight, and diarrhoea complications were monitored until recovery or for 14 days. RESULTS: A proportional hazards regression model controlling for age, diarrhoea aetiology, and severity of dehydration on admission revealed that the frequently fed group had a significantly shorter duration of diarrhoea (hazards ratio, 1.29; 95% confidence interval, 1.002 to 1.653). Frequently fed infants had a significantly greater weight gain and significantly lower faecal frequency and faecal weight. CONCLUSIONS: Breast feeding remains the preferred method of feeding infants with acute diarrhoea, but feeding cows' milk to adequately nourished infants with acute diarrhoea is safe and is more rapidly effective if provided in frequent feeds with low energy loads.

Acute Disease↗

PubMed1999

Application of YLD calculation in assessing disease data--an analysis of 4 diseases in 2 regions.

The objective of the current study is to discuss the problems related to how data is used to calculate Years Lost with Disability (YLD) with the method recommended by the World Bank. The study includes collecting useful data, estimating disease duration and average age of disease onset, adjusting incidence and prevalence data by means of a software programme, DISMOD (Harvard University Incidence & Prevalence Model), and assessing the importance of YLD calculation for different diseases. Remission and fatality rates of 3 diseases were estimated by experts at 2 round consultations. Incidence rates, disease duration and average age of disease onset were calculated and adjusted by DISMOD. YLD due to schizophrenia is the highest among 4 diseases in two regions. YLD is 18.88% in disability adjusted life year for 4 diseases in Xiacheng District, and 19.97% in Fuyang County. Available data can be used for the calculation of YLD after being adjusted. DISMOD is a useful instrument to test the internal consistency of incidence, prevalence, remission and fatality rate. The adjusted data are acceptable to experts and DISMOD. To get rational remission and fatality rates, we can use a cohort method through expert consultations. To reflect overall burden of disease, YLD calculation should be used.

Accidents, Traffic↗

PubMed1998

Aortocoronary bypass grafting with expanded polytetrafluoroethylene: 12-year patency.

Prosthetic coronary artery bypass conduits are rarely used because the rate of thrombosis is inherently higher than that with autologous conduits. The low medium-term patency rates of prosthetic grafts have restricted their use primarily to patients with inadequate autologous conduits or to selected emergencies. We describe a patient treated with expanded polytetrafluoroethylene who had documented patency 12 years after the operation.

Anastomosis, Surgical↗

PubMed1998

Endothelial sodding of the Permaflow prosthetic coronary artery bypass conduit.

BACKGROUND: Experiments were designed to determine the feasibility of sodding an endothelial monolayer within the lumen of a prosthetic conduit applied to the canine coronary circulation. METHODS: Autologous endothelial cells were sodded onto the luminal surface of the Permaflow conduit and immediately implanted to bypass the left circumflex coronary artery in adult mongrel dogs (n = 9). Unsodded Permaflow conduits were implanted as controls (n = 8). At 3 weeks, grafts were explanted and examined by scanning electron microscopy and immunostained for canine von Willebrand factor. RESULTS: Sodded grafts contained a confluent endothelial cell layer devoid of adherent thrombus or platelets and stained positively for canine von Willebrand factor. Unsodded grafts contained no endothelium and retained adherent platelets, collagen, and fibrin. Effluent from sodded grafts stimulated with calcium ionophore A23187 caused a significantly greater relaxation of its bioassay ring than effluent from unsodded grafts (60%+/-21% versus 12%+/-5%; n = 8, p < 0.03). CONCLUSIONS: Sodding of endothelial cells onto a Permaflow coronary artery bypass graft results in a confluent, viable, nonthrombogenic, endothelial monolayer and releases vasodilator substances in response to calcium ionophore A23187. Endothelial sodding may optimize prosthetic grafts.

Animals↗

PubMed1998

Gastric trichobezoar: case report and literature review.

Bezoars are conglomerates of food or fiber in the alimentary tract of humans and certain animals, mainly ruminants. In adults, bezoars are most frequently encountered after a gastric operation, but in children, bezoars are associated with pica, mental retardation, and coexistent psychiatric pathologic disorders. We describe a 4-year-old girl with trichotillomania in whom a gastric trichobezoar resulted in failure to gain weight, iron deficiency anemia, and a painless epigastric mass. The causes of gastric bezoars are discussed, with emphasis on diagnostic considerations, treatment options, and preventive measures.

Bezoars↗

PubMed1998

Identification and mapping of the amorphous phase in plasma-sprayed hydroxyapatite coatings using scanning cathodoluminescence microscopy.

The presence and distribution of the amorphous phase is a key factor in the performance and bone-bonding behavior of plasma-sprayed hydroxyapatite coatings. Microanalysis of coatings was conducted with microprobe Raman and scanning cathodoluminescence microscopy. It was confirmed that the darker regions in polished cross sections represent the amorphous phase. The more intense cathodoluminescence emission from the amorphous phase during electron-beam irradiation compared with the crystalline phase was used to detect the two structurally different areas within the sample. By selecting the peak of the emission at 450 nm it was possible to raster the surface with the electron beam and produce a map of the amorphous phase in polished sections, a fracture surface and an as-sprayed surface of the plasma-sprayed coating. Cathodoluminescence microscopy, based on the different light emission from the amorphous phase and hydroxyapatite, is a useful tool for identifying and mapping of the amorphous-phase constituent in plasma-sprayed coatings.

Journal Article↗

PubMed1998

Evidence that male smoking affects the likelihood of a pregnancy following IVF treatment: application of the modified cumulative embryo score.

Female cigarette smoking has been implicated as having a detrimental effect on in-vitro fertilization (IVF) outcomes mediated through: (i) a diminished ovarian reserve (DOR), and (ii) an elevated pregnancy loss. Research is sparse regarding the effect of male smoking. The objective of this retrospective cohort study was to investigate the effect of male and female smoking on: (i) the collective quality of embryos selected for uterine transfer, and (ii) the likelihood of achieving an ongoing pregnancy at 12 weeks. A total of 498 consecutive IVF treatment cycles were analysed. Female smokers were significantly younger (P < 0.05) and achieved a better modified cumulative embryo score (mCES) (P < 0.05) than female non-smokers. Female age correlated inversely with the number of oocytes collected (r = -0.42, P < 0.01) and the number of oocytes in turn was important in terms of predicting mCES. The decreasing number of oocytes aspirated with increasing age was of a significantly stronger magnitude for female smokers than for female non-smokers (P < 0.05). Multiple logistic regression was used to determine whether smoking affected the likelihood of achieving a 12-week pregnancy. The mCES, tubal infertility and male smoking were found to be significant. Male smoking interacted with male age (P = 0.0164), indicating for male smokers a decrease of 2.4% in the likelihood of achieving a 12-week pregnancy with every 1-year increase in age. This is the first study to show that male smoking has a deleterious effect on pregnancy outcome among IVF patients. Our study supports the increased risk of DOR but fails to support the elevated incidence of pregnancy loss among female smokers. A reduced pregnancy rate was associated with male smoking possibly through pre-zygotic genetic damage. The growing realization of a paternal component of reproductive impairment suggests that studying the male is necessary.

Cohort Studies↗

PubMed1998

Comparison of schizophrenic patients' families and normal families in China, using Chinese versions of FACES-II and the Family Environment Scales.

The lack of measures that systematically evaluate the characteristics and functioning of Chinese families is hindering the development of appropriate family interventions for schizophrenia in China. We assessed the reliability and validity of revised and adapted Chinese versions (CV) of the Family Adaptability and Cohesion Evaluation Scales (FACES-II-CV) and the Family Environment Scales (FES-CV) and administered these instruments to 120 respondents from families with a schizophrenic member and 126 respondents from control families. The psychometric properties of the FACES-II-CV and of the FES-CV Cohesion, Conflict, Intellectual-Cultural Orientation, and Active-Recreational Orientation scales are satisfactory, so they are appropriate for use in China; the remaining six FES-CV scales require further culturally appropriate revision. Compared to control families, families with schizophrenic patients in China have higher conflict, lower cohesion, poor adaptability, and are less likely to be involved in intellectual and recreational activities. These differences remained significant after adjusting for family and respondent characteristics.

Adaptation, Psychological↗

PubMed1997

Transcellular and extracellular impedances of the intact abdomen in putrefying rat cadavers.

Total (Zt) and extracellular (Ze) abdominal impedances of putrefying rat cadavers, stored at 18.0 +/- 0.7 degrees C, were measured at 50 kHz and at 1 kHz, respectively, during the first 7 days of death. Transcellular impedance was calculated from the measured values of Zt and Ze. Total impedance and Ze increased during the first day, and then decreased with increasing postmortem interval, while Zi remained unchanged during the first 3 days before increasing more than 4-fold between 3 and 7 days postmortem. These changes are consistent with net gain of electrolyte by the extracellular fluids and with degeneration of cell membranes which occur postmortem. It is concluded that, during putrefaction, Ze is a potentially more useful index of postmortem interval than Zt or Zi, and that measurement of total abdominal impedance at 50 kHz, rather than at 10 kHz, markedly improves the precision and accuracy of impedance measurement.

Abdomen↗

PubMed1997

Changes in the resistive and reactive components of abdominal impedance during the 1-21 day post-mortem periods in rats.

The magnitudes of the resistive (R) and reactive (X) components of total abdominal impedance (Zt) at 10 kHz, and of transcellular impedance (Zi), cytoplasmic impedance (Ri) and cell membrane capacitance (C), were calculated from sequential measurements of Zt, phase angle (theta) and extracellular impedance (Ze), in each of eight rat cadavers maintained at 9.0 +/- 1.5 degrees C. Total impedance, theta, R, X, Ze and Ri increased during the first 3 days of death, while C decreased. Thereafter, each of these parameters decreased with increasing post-mortem interval. The data indicate that Zt was predominantly resistive, and that Zt became progressively more resistive, and less reactive, with increasing time since death. Transcellular impedance remained relatively constant during the first 9 days, prior to increasing to more than 160% of its initial (3 h) value at 21 days post-mortem. This change coincided temporally with, and was attributable to, a time-dependent decrease in cell membrane capacitance post-mortem. Further studies, using human post-mortem tissues or body segments, will determine whether or not time-related changes in one or more of the impedance parameters may be used to estimate post-mortem interval.

Abdomen↗