Showing papers by "University of Peradeniya published in 2002"

Tobacco use and oral hygiene as risk indicators for periodontitis.

Abstract: Objective To detect the periodontal status of male smokers and betel chewers in a rural community in Sri Lanka and compare it with that of male non-tobacco users of the same community. Methods A cross-sectional community based study was carried out in a sample of 2277 rural adult males aged 20-60 years, adopting multistage cluster sampling technique. The present analysis was confined to 2178 subjects who were mutually exclusive smokers, betel chewers or non-tobacco users. The periodontal status was assessed by clinical measurement of levels of bacterial plaque (PLI), gingival inflammation (GI) and loss of epithelial attachment (LA). All measurements were carried out on four sites of all teeth present except third molars and the mean values for periodontal parameters were calculated. Results Bivariate analysis revealed that the overall periodontitis levels were significantly higher in betel chewers and smokers than in non-tobacco users. Multiple linear regression analysis showed that there were no significant effects of smoking and betel chewing per se on LA, independent of age, socioeconomic status (SES) and whether or not controlled for PLI. The effect of the quantified tobacco use on LA was statistically significant regardless of age, PLI or SES. However, the effect of the quantified tobacco use was considered limited when compared to that of oral hygiene. Conclusions The findings highlighted the importance of oral hygiene in the aetiology of periodontitis while confirming the statistical significance of the quantified tobacco use on LA. Oral hygiene and the quantified tobacco use may be considered as risk indicators for periodontitis.

Multiple car-following data with real-time kinematic Global Positioning System

Abstract: The real-time kinematic differential Global Positioning System (GPS) has facilitated a new horizon in traffic engineering. Multiple car-following experiments conducted with a real-time kinematic GPS with 10 vehicles participating in a probing field gave high-quality results in headway, speed, relative speed, and acceleration. The expected accuracies for measuring position and speed were 10 mm and 0.16 km/h, respectively. The vehicles were driven in a loop consisting of two parallel straight sections connected by two semicircular curves. Different driving conditions were induced in the platoon by instructing the leading driver to follow predetermined speed variations. The experiments yielded sets of continuous observations. Headway, speed, and acceleration were measured using conventional equipment for the purpose of comparing accuracy. The accuracy of the data obtained using the GPS was superior to that of the same data obtained using conventional measurements. The variation in driving characteristics down the stream of vehicles was studied using the experimental data. The results showed that the reaction time between a change in relative speed and the corresponding change in acceleration varies during the driving process. The reaction time of individual drivers also changes along the platoon. The good-quality data were able to give high-resolution plots of acceleration and relative speed illustrating that both the reaction time and the functional relationship between acceleration and relative speed do not remain constant.

Biocontrol activity and induced resistance as a possible mode of action for Aureobasidium pullulans against grey mould of strawberry fruit

Abstract: Efficacy and mode of action were investigated fox Aureobasidium pullulans, a potential biocontrol agent for grey mould on strawberry fruit. Wound inoculation of detached green strawberry cv. Elsanta fruit with Aureobasidium pullulans prevented grey mould rot on fruit inoculated 2 days later with Botrytis cinerea. Treatment of white, pink and red-ripe fruit did not, however, control grey mould. Treatment of wound sites on green fruit with both live and heat-killed A. pullulans cells reduced B. cinerea infection compared to controls. Dip-inoculation of unwounded green strawberry fruit with A pullulans when still attached to the plant delayed the development of grey mould after harvest at the fully ripe stage. The (i) efficacy of A. pullulans on green but not on ripening fruit, (ii) partial inhibitory effect of both live and heat-killed A. pullulans cells and (iii) absence of evidence for antibiotic production from in vitro competition tests suggest that control of grey mould on green fruit is at least partly due to a mechanism other than antagonism and / or competition. Bioassays showed that skin tissue from green fruit treated with A. pullulans had greater antifungal activity than control tissue. Thus, enhanced natural disease resistance in green strawberry fruit contributed to grey mould rot suppression by A. pullulans.

Upregulation of human beta-defensin 2 peptide expression in oral lichen planus, leukoplakia and candidiasis. an immunohistochemical study.

Abstract: Human beta defensin 2 (hBD-2) is a major antimicrobial peptide that is produced by many types of epithelial cells, and is transcriptionally inducible by various proinflammatory agents, such as cytokines and bacteria. Although in vitro studies of the hBDs in oral epithelial cells have been well documented, only little is known about the in vivo pathological state of oral epithelium. We investigated the localization of hBD-2 peptide in tissue sections of oral lichen planus, leukoplakia, candidal leukoplakia and radicular cysts using immunohistochemistry. HBD-2 was stained in both the hyperkeratinized and the granular layers in cases of lichen planus with hyperkeratosis and leukoplakia. Expression in spinous and suprabasal layers was often strong in lichen planus. There were no significant differences in the number of S-100 positive dendritic cells between the widely stained areas and those with limited staining areas in lichen planus. In cases of candidal leukoplakia, the hyphae of candida were mainly detected on the surface of keratinization, which showed only negative or faint staining for hBD-2. These results suggest that hBD-2 is vigorously induced by lichen planus-related inflammation and that it plays an important role in protection from Candida albicans infection; however, it is not a strong chemotactic attractant for Langerhans cells in pathological conditions of oral epithelium.

Dental Caries and Developmental Defects of Enamel in Relation to Fluoride Levels in Drinking Water in an Arid Area of Sri Lanka

Abstract: The study was conducted to assess caries and developmental defects of enamel in relation to fluoride levels in drinking water and the association between caries experience and the severity of diffuse

Groundwater quality in the Valigamam region of the Jaffna Peninsula, Sri Lanka

Abstract: Abstract The Valigamam region is underlain by a Miocene limestone formation and a highly porous soil cover. The region is totally dependent on groundwater to meet its agricultural, industrial and domestic needs, since other sources of water are seasonal. Recharge from rainfall is limited by high run-off and evapotranspirational losses. The region experiences water supply problems due to high concentrations of chloride, total hardness and nitrate in groundwater. The spatial distribution of chloride varies from year to year, with maximum concentrations experienced during or after the wet season. The major factor explaining high chloride concentrations is the excessive extraction of groundwater that results in saline intrusion from the sea or lagoonal areas. In a large proportion of wells sampled for nitrate, levels exceed the WHO standard due to intensive agricultural practices involving very high inputs of artificial and natural fertilizers and the improper construction of latrine soakaway pits. To improve groundwater quality in the Jaffna Peninsula will require controls on the location of new wells, a revision of existing and future pumping rates and a change in agricultural practices. It is imperative that future work in the region should focus on combining groundwater management and sustainable agricultural practice.

Propanil‐resistant barnyardgrass [Echinochloa crus‐galli (L.) Beauv.] in Sri Lanka: Seedling growth under different temperatures and control

Abstract: Experiments were conducted to (i) evaluate the efficacy of propanil formulations available in Sri Lanka in controlling Echinochloa crus-galli ; (ii) study the seedling growth of propanilresistant (R) and -susceptible (S) biotypes of the weed under different temperatures; (iii) quantify the level of resistance in R biotypes and; (iv) to suggest alternative control measures for R biotypes. Field studies showed that retail propanil formulations (36% a.i., EC) applied at 2.7 kg a.i. ha - 1 gave less than 30% control of E. crus-galli collected from several locations of the north dry zone of Sri Lanka. Chemical analysis revealed that there was no adulteration of propanil formulations at the retailer level. Growth studies conducted in controlled environments indicated that per cent germination and seedling growth of R and S biotypes were similar at the day/night temperature regimes imposed. However, per cent germination for plants grown under a 34/31 ∞ C (day/night) regime was 27‐29% higher compared to those grown at 28/ 24 ∞ C. At the higher temperature regime, R and S biotypes reached the 2‐3 leaf stage five days earlier, and the 4‐5 leaf stage seven days earlier. The ED 50 values from the dose‐response experiments indicated that the R biotype was four times more resistant to propanil than susceptible ones. The resistance index (RI) did not vary significantly under different temperature regimes. Quinclorac (25% a.i., SC) applied at 200 g a.i. ha - 1 and bispyribac-sodium (10% a.i., SC) applied at 30 g a.i. ha - 1 (recommended dosages) successfully controlled propanil-resistant biotypes of E. crus-galli . Conversely, oxadiazon and propanil (8% and 23% a.i., EC, respectively) applied at 280 + 805 g a.i. ha - 1 did not result in satisfactory control.

The physiological basis of increased biomass partitioning to roots upon nitrogen deprivation in young clonal tea (Camellia sinensis (L.) O. Kuntz)

Abstract: Deprivation of nitrogen (N) increases assimilate partitioning towards roots at the expense of that to shoots This study was done to determine the physiological basis of increased root growth of tea (sCammellia sinensis L) under N shortage Nine-month-old clonal tea (clone TRI2025) was grown in quartz sand under naturally lit glasshouse conditions Three levels of N (0, 375 and 75 mM N) were incorporated in to the nutrient solution and applied daily Plant growth, photosynthesis, root respiration and plant N contents were measured at 10-day intervals over a 45-day period Root dry weight showed a sharp increase during the first 15 days after the plants were transferred to 0 mM N, whereas no such increase was shown in plants transferred to 75 mM N In contrast, shoot dry weight increased at 75 mM N and was significantly greater than at 0 mM N, where no increase was observed Due to the above changes, root weight ratio increased and leaf weight ratio decreased during the first 15 days of N deprivation Leaf photosynthetic rates did not vary between N levels during the initial 15-day period Thereafter, photosynthetic rates were greater at 75 mM and 375 mM N than at 0 mM N Root respiration rate decreased at 0 mM N, whereas it increased at 375 and 75 mM N, probably because of the greater respiratory cost for nitrate uptake Root respiratory costs associated with maintenance (R m) and nitrate uptake (R u) were calculated to investigate whether the sharp increase of root growth observed upon nitrogen deprivation was solely due to the reduced respiratory costs for nitrate uptake The estimated values for R m and R u were 3241 × 10−4 μmol CO2 g−1 (root dry matter) s−1 and 064 mol CO2 (mol N)−1, respectively Calculations showed that decreased respiratory costs for nitrate uptake could not solely account for the significant increase of root biomass upon N deprivation Therefore, it is concluded that a significant shift in assimilate partitioning towards roots occurs immediately following N deprivation in tea

Effects of artificial shade on attack by the mahogany shoot borer, Hypsipyla robusta (Moore)

Abstract: Swietenia macrophylla King (Meliaceae: Swietenioideae) provides one of the premier timbers of the world. The mahogany shoot borer Hypsipyla robusta Moore (Lepidoptera: Pyralidae) is an economically important pest of S. macrophylla throughout Asia, Africa and the Pacific. No viable method of controlling this pest is known. Previous observations have suggested that the presence of overhead shade may reduce attack by H. robusta, but this has not been investigated experimentally. This research was therefore designed to assess the influence of light availability on shoot-borer attack on S. macrophylla, by establishing seedlings under three different artificial shade regimes, then using these seedlings to test oviposition preference of adult moths, neonate larval survival and growth and development of shoot borer larvae. Oviposition preference of shoot borer moths was tested on leaves from seedlings grown under artificial shade for 63 weeks. A significant difference in choice was recorded between treatments, with 27.4 ± 1.5 eggs laid under high shade and 87.1 ± 1.8 under low shade. Neonate larval survival on early flushing leaflets of S. macrophylla did not differ significantly between shade treatments. Larval growth rate, estimated by measuring daily frass width, was significantly higher for those larvae fed on seedlings from the high and medium shade treatments (0.1 mm/day), than the low shade treatment (0.06 mm/day). In laboratory-reared larvae, the total mass of frass produced was significantly higher in the high shade treatment (0.4 g) than under the low shade treatment (0.2 g). Longer tunnel lengths were bored by larvae in plants grown under high shade (12.0 ± 2.4 cm) than under low shade (7.07 ± 1.9 cm). However, pupal mass under low shade was 48% higher than that under the high shade treatment, suggesting that plants grown under high shade were of lower nutritional quality for shoot borer larvae. These results indicate that shading of mahogany seedlings may reduce the incidence of shoot borer attack, by influencing both oviposition and larval development. The establishment of mahogany under suitable shade regimes may therefore provide a basis for controlling shoot borer attack using silvicultural approaches.

Growth and development of Cuscuta chinensis Lam. and its impact on selected crops

Abstract: The growth and development of Cuscuta chinensis Lam., and the effects of the holoparasite on the growth and yield of tomato ( Lycopersicon esculentum ), chilli ( Capsicum annuum ) and rice ( Oryza sativa ) were investigated in pot experiments under glasshouse conditions. ‘Mature’ and ‘immature’ seeds of C. chinensis showed 15 and 47% germination, respectively. The independent life duration of seedlings from ‘immature’ seeds was 6 days shorter than ‘mature’ seeds (19 days). Cuscuta chinensis formed haustoria on chilli and tomato, but not on rice seedlings. Infection with three C. chinensis seedlings per host plant reduced leaf area, dry weight, carbon and nitrogen content by 78‐84% and 27‐44% in tomato and chilli plants, respectively. Dry weight of C. chinensis was 0.63 g per pot in tomato, and 0.24 g per pot in chilli. Carbon and nitrogen content of C. chinensis was 0.189 and 0.028 g per pot, respectively, when grown with tomato. When it was grown with chilli, the carbon and nitrogen content of C. chinensis was 0.001 and 0.007 g per pot, respectively. Cuscuta chinensis reduced the fruit yield of tomato and chilli by 72 and 29%, respectively. The results indicated that tomato is a preferred host of C. chinensis compared with chilli, and rice is not preferred. In the host‐parasite associations, C. chinensis suppressed growth and yield of chilli and tomato by diverting the elaborated products of metabolism of the hosts.

The structure of the O-chain of the lipopolysaccharide of a prototypal diarrheagenic strain of Hafnia alvei that has characteristics of a new species under the genus Escherichia.

Abstract: The structure of the O-polysaccharide of the lipopolysaccharide from a diarrheal strain isolated in Bangladesh was studied with sugar, and methylation analysis, NMR spectroscopy, mass spectrometry and partial acid hydrolysis. The strain was first designated as Hafnia alvei, but later found to be a possible new species in the genus Escherichia. Two different polysaccharides were detected, a major and a minor one. The structure of the major polysaccharide is given below, while the structure of the minor one was not investigated. The structure of the repeating unit was established as The structure does not resemble any of the previously investigated lipopolysaccharide O-chains from Escherichia coli or H. alvei, but could fit in either group based on types of sugar residues and acidity. Phenotypic microbiological studies cannot definitely assign it to either species of the two genera. Genetic hybridization studies indicate that the Bangladeshi isolates may require a new species designation under the genus Escherichia.

Information gathering behaviour of arts scholars in Sri Lankan universities: a critical evaluation

Abstract: Describes the results of an investigation on the information gathering behaviour of arts scholars in Sri Lanka’s universities. The method involves a questionnaire to collect both qualitative and quantitative data and descriptive statistical methods were applied in the analysis of data. The overall response rate was around 70 per cent and each university was considered as a cluster. Arts scholars gather information for three basic types of activities; teaching, research and administration. The respondents spend 45‐55 per cent of their time in the library and the majority ranked “to keep up with current developments” as the main reason for seeking information. In comparison to scientists, arts scholars appear to use publishers’ catalogues as the most important source for new developments in their relevant fields. Many do not use index card files or outside assistance in searching literature.

The Clinical Interview Schedule - Sinhala version: validation in a community setting in Sri Lanka

Abstract: The Clinical Interview Schedule – Revised (CIS-R) was validated in a clinic setting for adolescents 15–19 years of age in Sri Lanka. The interview schedule was translated into Sinhala and modified to include sections introducing each symptom group. One-hundred-and-thirty-one adolescents attending a psychiatric clinic for the first time were interviewed by a lay interviewer using CIS-R (Translated). They had previously been examined and rated by a psychiatrist using local (emic) diagnostic procedures. All the filtering questions showed a high level of sensitivity (80%–96%). None of the questions in the sleep problems and phobias sections were effective at discriminating between those who did and did not show significant symptoms in these areas according to the psychiatrist. The internal consistency of the sections of the interview schedule (when these two sections were excluded) varied between 0.60 and 0.82. Linear regression showed that, when both sections were excluded, 97% of the variation of total score could be explained. Therefore, it was decided to exclude the sleep problems and phobias sections from the modified interview schedule. As the population samples are likely to be different from clinic samples it is necessary to test the validity again in a community sample before confirming the validity of the modified interview schedule. Copyright © 2002 Whurr Publishers Ltd.

The impact of polyene, azole, and DNA analogue antimycotics on the cell surface hydrophobicity of Candida albicans and Candida tropicalis in HIV infection.

Abstract: Oral candidiasis is the most common opportunistic infection in individuals infected with the human immunodeficiency virus. Though Candida albicans is the major aetiological agent, non-albicans species such Candida tropicalis are now emerging as important agents of such infection. The Candida cell surface hydrophobicity (CSH) is considered a critical factor contributing to its colonization potential and virulence. It is also known that brief exposure to sub-cidal concentrations of antifungal agents is a likely scenario in the oral environment where the administered drugs are diluted continuously due to the flushing action of saliva. Hence the objective of the present study was to compare the CSH of 10 isolates each of C. albicans and C. tropicalis from HIV-infected individuals following brief exposure (1hour) of isolates to sub-therapeutic concentrations of nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine. The CSH was assessed by a previously described biphasic aqueous-hydrocarbon assay. The mean percentage reduction of CSH of C. albicans following brief exposure to nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine was27.33 (p 0.05), 18.4 (p > 0.05) and 14.64 (p > 0.05) respectively. The mean percentage reduction of CSH of C. tropicalis following brief exposure to nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine was 33.81 (p 0.05), 21.53(p > 0.05) and 17.68 (p > 0.05) respectively. A significant inter-species variation in CSH was observed for nystatin and amphoterecin B. Overall the results reveal that the CSH of C. albicans is affected to a significantly lesser degree compared with C. tropicalis when exposed to the antifungals. These data further illustrate another mode of action of antifungals on Candida leading to a reduction in the CSH and thereby the yeast adherence to host tissues.

Lymphadenitis, trans-epidermal elimination and unusual histopathology in human rhinosporidiosis.

Abstract: From a study of rhinosporidial tissues of 64 human cases of ocular, urethral and nasopharyngeal disease, unusual histopathological features of 27 cases are described. Histopathological evidence of lymphadenitis in rhinosporidiosis is presented for the first time. The phenomenon of `trans-epidermal elimination' of sporangia of the causative pathogen Rhinosporidium seeberi is illustrated and it is argued that this phenomenon is rather the pathogen's mechanism for endospore-dispersal than a non-specific defence reaction of the host as has previously been suggested. Other unusual appearances described include variations in the intensity and composition of the host-cell infiltrate in tissues from different patients and in different portions of the same tissue, pitfalls in histopathological diagnosis, and unusual appearances of the pathogen. Histopathological clues to the pathogenesis of rhinosporidiosis and mechanisms of anti-rhinosporidial immunity in the host are discussed, illustrating the probable occurrence of immunesuppressive reactions to account for the variations in the density and composition of the host-cell infiltrate and the state of the rhinosporidial sporangia – intact or degenerate –, relating these variations to the chronicity, recurrences and systemic dissemination of rhinosporidiosis.