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Biomedical subjects

S Weerasinghe

Publications and source records attributed to S Weerasinghe.

15 recordsLinked to original sources
PubMed2006

Cumulative sum (CUSUM) analysis in the assessment of trainee competence in fetal biometry measurement.

OBJECTIVE: To determine the value of cumulative sum (CUSUM) analysis in assessing trainee proficiency in fetal biometry measurement. METHODS: Three primary healthcare doctors with no prior ultrasound training were recruited. Each trainee measured the fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) on 100 consecutive pregnant women. The supervisor repeated the measurements. The CUSUM for each set of trainee measurements was calculated at a set failure rate of 10%. The point at which the graph fell below two consecutive boundary lines indicated the number of examinations required to achieve competence. RESULTS: The CUSUM graphs showed that the rate of learning measurement skills varied among the three trainees. The graph for the CUSUM series for BPD and HC measurement for all trainees fell below two consecutive boundary lines and remained there, indicating competence. The CUSUM series for AC measurement for two of the trainees indicated that competence was achieved; however, for the third trainee, while the graph fell below two consecutive boundary lines, indicating competence, it rose again, crossing two consecutive boundary lines. This indicated a loss of competence and the need for further training. FL measurements for the same trainee never fell below two consecutive boundary lines, indicating failure to achieve competence; the other two achieved competence, but failed to maintain it. CONCLUSIONS: CUSUM is a useful tool for identifying points of competence and for quantifying the duration of ultrasound training required for each trainee. It provides an early indication of performance, and highlights difficulties in individual performance.

Abdomen↗
PubMed2000

The health and nutritional status of school children in two rural communities in Sri Lanka.

There is growing evidence of considerable burden of morbidity and mortality due to infectious diseases and undernutrition in school children. This study describes the nutritional status and parasitic infections of school children in two areas of rural Sri Lanka. All children in four primary schools in the Moneragala district of Sri Lanka were included in the study. The height and weight of children were measured and anthropometric indices calculated. Stool and blood samples were examined for evidence of intestinal helminthiasis, malaria and anaemia. A greater proportion of boys than girls were underweight, wasted and stunted. Over 80% of the children were anaemic but did not apparently have iron deficiency anaemia according to their blood picture. The prevalence of parasitic infections such as hookworm and Plasmodium spp that may contribute to anaemia was low.

Body Weight↗
PubMed2000

The dietary habits of idiopathic calcium stone-formers and normal control subjects.

OBJECTIVES: To examine the relationship between 12 macro- and micro-nutrients and the risk of recurrent calcium stone formation by comparing the diets of a large outpatient clinic-based group of patients who had formed calcium-based urinary tract calculi with that of a population-based control group matched for age, gender and body mass index. PATIENTS, SUBJECTS AND METHODS: The dietary intake of 500 patients (cases) randomly selected from the adult population attending an outpatient renal-stone clinic and being evaluated and/or treated for biochemically or radiologically diagnosed calcium-based upper urinary tract calculi were compared with those of 500 control subjects selected to match for age, sex and body mass index from a stratified probability sample of 2212 adults (not institutionalized) living in the same geographical area. RESULTS: Comparing the mean nutritional intakes showed a statistically higher consumption of energy, carbohydrates, sodium, fibre, vitamin C, fat and folic acid among cases than in controls. The intake of calcium, alcohol and vitamin A was significantly higher among the controls. There were no significant differences in the intake of protein, niacin or iron. The results of these comparisons varied when the groups were stratified by sex, age and body mass index. CONCLUSIONS: Dietary risk factors for calcium-based urinary tract calculi are many and complex, and a detailed consideration of sex, age and body mass index is important in interpreting such data. While it is difficult to draw firm conclusions about causes and effects of individual nutrients from the available data, this study indicates a possibly more important role for dietary fat in stone formation than has been previously recognized. This relationship needs to be further explored in relation to urinary risk factors, as it may be possible to advise patients to reduce dietary fat as a prophylactic measure for stone formation. As dietary fat has been associated with cardiovascular diseases and possibly cancer, an overall recommendation to these patients for a low dietary fat intake may be easier to follow.

Adult↗
PubMed2000

Enhancement of survival of stored dopaminergic cells and promotion of graft survival by exposure of human fetal nigral tissue to glial cell line--derived neurotrophic factor in patients with Parkinson's disease. Report of two cases and technical considerations.

The authors have studied the ability of glial cell line-derived neurotrophic factor (GDNF) to promote survival of human fetal dopaminergic tissue after a storage period of 6 days and subsequent implantation into the human putamen. The results indicate that GDNF promotes survival of stored dopaminergic cells. Cells stored without GDNF had a 30.1% decrease in survival time compared with those exposed to GDNF. Two patients with Parkinson's disease received bilateral putaminal implants of fetal dopaminergic cells exposed to GDNF for 6 days and showed enhancement of graft survival as assessed by positron emission tomography scanning. A mean increase of 107% in putaminal fluorodopa uptake from baseline values was observed 12 months postgrafting.

Aged↗
PubMed1996

Self-assessment of disease activity by patients with rheumatoid arthritis.

OBJECTIVE: To determine the reliability of self-assessment of disease by patients with rheumatoid arthritis (RA), with a particular emphasis on the assessment of articular swelling. METHODS: A questionnaire was developed using components from validated instruments. Information was obtained on global function, global joint tenderness/swelling, and joint pain (10 cm visual analog scales), duration of musculoskeletal morning stiffness (grade 1-6), ACR functional score (grade 1-4), tender joint count (0-20), tender joint score (0-60), swollen joint count (0-20), and swollen joint score (0-60). Data were collected prospectively on 61 patients with RA in a teaching clinic or office practice by 4 staff rheumatologists. Patient questionnaires were completed within 24 h before physician assessments. Followup assessments were carried out on 27 patients after a mean interval of 3 months (range 0.5-6). RESULTS: At the initial assessment there was a significant correlation between patient and physician assessments for global function (r = 0.83; p = 0.01) [intraclass correlation coefficient (ICC) = 0.83; p < 0.01], global joint tenderness/swelling (r = 0.83; p < 0.01) (ICC = 0.83; p < 0.01), global joint pain (r = 0.83; p < 0.01) (ICC = 0.81; p < 0.01), duration of morning stiffness (r = 0.83; p < 0.01) (ICC = 0.85; p < 0.01), ACR functional score (r = 0.61; p < 0.01) (ICC = 0.62; p < 0.01), tender joint count (r = 0.57; p < 0.01) (ICC = 0.31; p < 0.01), and tender joint score (r = 0.60; p < 0.01) (ICC = 0.35; p < 0.01). However, there was poor correlation between patient and physician assessments for both swollen joint count (r = 0.16; p > 0.05) (ICC = -0.02; p > 0.05) and swollen joint score (r = 0.24; p > 0.05) (ICC = 0.12; p > 0.05). Longitudinal analysis indicated significant correlation between changes in patient and physician assessments in all variables except swollen joint count and score. CONCLUSION: Although there was good correlation between most variables for patient and physician assessments of disease activity in RA, there were substantial differences in the assessment of joint swelling. This objective determinant of disease activity cannot be ascertained in self-report measures of health status.

Adult↗
PubMed1995

Structure and stability of a model pyrimidine-purine-purine DNA triple helix with a GC.T mismatch by simulation.

A 1.5 ns long molecular dynamics simulation was conducted to compare the structure and stability of a model DNA triplex in saline solution with that found from experiments. The model DNA was an antiparallel py.pu.pu (CG.G) 7-mer structure which contained a GC.T mismatch triplet at the middle of the sequence. The local conformation of the mismatch triplet and the effects of this triplet on the global helical structure suggest that the GC.T triplet forms stable hydrogen bonds and shows distortions from an in-plane alignment. The overall rms deviation of the triplex is similar to one without a mismatch, although the thymine base in the mismatch triplet shows significantly higher mobility. A high coordination probability for water between the G and T bases in the mismatch triplet was observed to have an effect on the stability of non-hydrogen-bonded base pairs. Average helical parameters, sugar pucker, and backbone dihedral angles indicate that the CG.G triplets on the 3' side of the mismatch triplet possess different structural and dynamical properties than that of the 5' side. These observations are consistent with recently available experimental results and provide an interpretation of the observed experimental structure. They also suggest that inclusion of explicit water molecules is necessary in order to understand and predict the interaction between the third strand and duplex DNA.

Computer Simulation↗
PubMed1995

Dielectric response of triplex DNA in ionic solution from simulations.

We have analyzed a 1.2-ns molecular dynamics simulation of 51 mM d(CG.G)7 with 21 Na+ counter-ions and 1 M NaCl in water. Via the dipole fluctuations, the dielectric constant for the DNA is found to be around 16, whereas that for the bases and sugars combined is only 3. The dielectric constant for water in this system is 41, which is much smaller than 71 for pure SPC/E water, because of the strong restriction imposed on the motion of water molecules by the DNA and the ions. Also addressed in the present work are several technical issues related to the calculation of the dipole moment of an ionic solution from molecular dynamics simulations using periodic boundary conditions.

DNA↗
PubMed1992

Method to estimate relative transmission efficiencies of Anopheles species (Diptera: Culicidae) in human malaria transmission.

A mathematical expression was derived to estimate the relative malaria transmission efficiency of an anopheline species with respect to a standard well-characterized species for which all vector parameters can be sufficiently determined. The method is particularly useful in situations where multiple anopheline species contribute to human malaria transmission and requires the estimation of the man-biting rate, the sporozoite rate, and the human malaria incidence. Under stable conditions of vector abundance, the average sporozoite rate in a species during a transmission season would by itself reflect its relative transmission efficiency. This "efficiency" then was used to calculate the "effective human-biting rate"; i.e., the human-biting rate of that species if it were to have ecological properties identical to those of the standard species. The standard well-characterized species then could be used with the effective human-biting rate of all species to quantify transmission, thus overcoming the need to measure vector parameters for all anopheline species contributing to transmission. An expression also was derived to calculate the relative contribution made by each species to malaria transmission. The usefulness of this method was illustrated using entomological and epidemiological data from Kataragama, Sri Lanka.

Animals↗
PubMed1992

Anti-circumsporozoite protein antibodies measure age related exposure to malaria in Kataragama, Sri Lanka.

Antibodies to two peptides DDAAD and (NANP)40 representing the repetitive sequence of circumsporozoite antigens (CS protein) of P. vivax and P. falciparum respectively were measured in a cohort of 149 and 107 individuals respectively at four, 6 monthly blood surveys performed on residents of Kataragama, a P. vivax malaria endemic region in southern Sri Lanka. The prevalence of antibodies to the CS protein of both species was relatively low being less than 20% to either peptide in the population as a whole, this being consistent with the low entomological inoculation rates in the area. A marked age related prevalence pattern was evident, with the prevalence of antibodies increasing with age to reach between 25 to 30% in the 25-50 year age group in both P. vivax and P. falciparum. The population had had a life long exposure to P. vivax malaria but not to P. falciparum, an epidemic of which occurred in this region a few months prior to the beginning of this study. Nevertheless, the age-related prevalence of these antibodies was identical with respect to the two species. This suggests that the age-related prevalence pattern reflected differences in inoculation rates between the age groups due to differences in exposure to inoculation rather than an age acquired response resulting from a cumulative experience over several years. An analysis of antibody prevalence in individuals showed first, that sporozoite inoculations must have been clustered rather than homogeneously distributed in the population and secondly, that sero-conversion did not correlate with malaria infections in these individuals.

Adolescent↗
PubMed1991

A mathematical model for Plasmodium vivax malaria transmission: estimation of the impact of transmission-blocking immunity in an endemic area.

We have developed a multi-state mathematical model to describe the transmission of Plasmodium vivax malaria; the model accommodates variable transmission-blocking/enhancing immunity during the course of a blood infection, a short memory for boosting immunity, and relapses. Using the model, we simulated the incidence of human malaria, sporozoite rates in the vector population, and the level of transmission-blocking immunity for the infected population over a period of time. Field data from an epidemiological study conducted in Kataragama in the south of Sri Lanka were used to test the results obtained. The incidence of malaria during the study period was simulated satisfactorily. The impact of naturally-acquired transmission-blocking immunity on malaria transmission under different vectorial capacities was also simulated. The results show that at low vectorial capacities, e.g., just above the threshold for transmission, the effect of transmission-blocking immunity is very significant; however, the effect is lower at higher vectorial capacities.

Animals↗
PubMedDate not supplied

Infectivity of Plasmodium vivax and P. falciparum to Anopheles tessellatus; relationship between oocyst and sporozoite development.

The assessment of malarial infectivity, for example in the evaluation of transmission blocking immunity, is generally based on counting oocysts in mosquitoes fed on infected blood. Ultimate transmission of the disease may, however, depend on the sporozoite load in the mosquito and its relationship to the size of the inoculum introduced to man. We conducted a laboratory study on Anopheles tessellatus infected with 108 different natural isolates of Plasmodium vivax from patients and 24 of P. falciparum to determine the relationship between oocyst numbers, sporozoite loads, and the effect of these on mosquito mortality. It was found that the P. vivax parasite density was positively correlated with the proportion of mosquitoes infected by a given feed at both the midgut and gland stages of parasite development (correlation coefficient [r] = 0.77, P < 0.001 and r = 0.6, P < 0.05 respectively). A significant positive linear correlation was observed between the number of oocysts and sporozoites in P. vivax (r = 0.5; P < 0.05); the proportions of mosquitoes infected with oocysts and sporozoites were also similarly related, although in general about 15% of mosquitoes infected with oocysts failed to develop salivary gland infections with sporozoites. The number of mosquitoes infected with P. falciparum parasites was too low for statistical analysis. Infection with either species of parasite did not appear to affect mosquito survival, nor was parasite density in the mosquito correlated with mosquito mortality.

Animals↗
PubMedDate not supplied

Features of recrudescent chloroquine-resistant Plasmodium falciparum infections confer a survival advantage on parasites and have implications for disease control.

This paper reports on the features of recrudescent infections of chloroquine-resistant Plasmodium falciparum (CQRPf) malaria from a study in vivo of patients from a malaria endemic (n = 527) and non-endemic (n = 129) region of Sri Lanka where the incidence of RI resistance was 30% and 55%, respectively. In both groups of patients, the recrudescent infections which emerged after treatment of the primary infection with chloroquine (CQ) and primaquine had significantly lower peripheral parasitaemia (0.036% and 0.108% in endemic and non-endemic patients, respectively) compared to their primary infections (mean parasitaemia 0.13% and 0.49%; P = 0.021 and 0.002, respectively). The recrudescences of CQ resistant infections also gave rise to clinical disease of markedly reduced severity (average clinical scores of 10.1 and 8.2) compared to their primary infections (average clinical scores of 12.4 and 12.3; P = 0.003 and 0.001, respectively, in endemic and non-endemic patients). CQ resistant recrudescent infections therefore had a lower probability of being diagnosed and treated. In endemic patients, a higher proportion of CQRPf infections (57%) had gametocytaemia compared to the chloroquine sensitive ones (29%) (P = 0.014, chi 2 = 5.96) and were significantly more infective to mosquitoes (P = 0.047). these findings imply that, in areas where CQ resistance is prevalent, the continued use of the drug may confer a survival and propagation advantage on resistant parasites and favour the rapid expansion of their reservoir. In support of this, we also present epidemiological evidence showing that, in endemic areas, the proportion of P. falciparum patients carrying gametocytes has increased significantly since the emergence of chloroquine resistance. These findings are relevant to the management of drug resistance and malaria control in countries where P.falciparum is only partially resistant to CQ.

Adolescent↗
PubMedDate not supplied

Incidence of cancer in Sydney and Cape Breton County, Nova Scotia 1979-1997.

The primary purpose of this study was to assess whether Sydney, Industrial Cape Breton County excluding Sydney (ICBxS) and Cape Breton County (CBCo) residents were at increased risk for cancer compared to Nova Scotia (NS) residents over five-year periods during 1979 through 1997. Gender-stratified, age-standardized cancer incidence rates were calculated following the direct method. All-cause rates were higher for female and male residents of Sydney, ICBxS and CBCo compared to NS based upon both municipality and postal code methods of residence classification. A sensitivity analysis of residential coding yielded a high degree of consistency for all geographies except Sydney, limiting comparisons of Sydney rates with other local geographies except where consistencies were observed. The results of this ecological study support the need for further analysis of factors contributing to the increased risk for cancer in CBCo.

Age Distribution↗