Biomedical subjects
Publications and source records attributed to M Fletcher.
This article describes results from one of the sites involved in a multi-centred comparative study designed to assess the performance of a collagen-alginate dressing used in the treatment of leg ulceration. The research methods used in the trial, as well as the results, will be of interest to practising nurses. Those involved in similar work are invited to submit articles to be considered for publication in future issues of this supplement.
An unlinked anonymous HIV antibody study of neonates, using surplus dried blood spots on Guthrie cards, was introduced as a means of estimating the prevalence of HIV infection in childbearing women. From March 1990 to February 1992, blood spots from 14,520 infants were tested for anti-HIV, using an HIV IgG antibody capture particle-adherence test; only one sample gave a confirmed positive reaction. This type of study involves no interference in routine care and can be operated without difficulty in a district general hospital setting where neonatal metabolic screening is performed.
A randomized controlled trial was carried out in Assab under the auspices of the National Organization for the Control of Malaria and other Vectorborne Diseases of Ethiopia to assess the effectiveness of an indigenous cyprinodontid fish, Aphanius dispar, in controlling mosquito larvae, including the local malaria vector, Anopheles culicifacies adanensis. Cisterns, wells and barrels were found to be important breeding sites for the malaria vector and for culicine mosquitoes. Fish were equally effective in controlling mosquito larvae in all the types of breeding site investigated. The overall proportion of sites with fish that harboured mosquito larvae was 1.6%, ranging from 1.5 to 1.7% according to type of site, as compared to 34% in sites left unstocked, ranging from 17.9 to 60.0%. Monthly restocking of fish where necessary was found to be sufficient to maintain an adequate level of control. Stocking of larvivorous fish in wells and household water storage containers was well-accepted by the participants, who were aware of the role of the fish in malaria prevention and found the fish useful in keeping their water free of other aquatic organisms. Based on the results of this study, larvivorous fish were introduced on an operational scale for the control of malaria transmission in Assab, with the voluntary participation of the population and the collaboration of the Municipality and health authorities of Assab.
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In Langerhans' cell histiocytosis, the prognostic significance of pulmonary disease is controversial. The clinical and radiological features and lung function tests of Langerhans' cell histiocytosis patients presenting to a single tertiary referral center between 1981 and 1987 were reviewed. Age at diagnosis ranged from 2 weeks to 16 years (median 1.7 years) and the male-female ratio was 2.4:1. No child presented with lung involvement alone. In 18 (40%) of 45 patients with multisystem disease there was clinical and/or radiological evidence of lung pathology. Another 6 children (13%) with normal chest roentgenograms had abnormal lung function tests, suggesting subclinical ("occult") involvement. Those with overt lung disease tended to present at a younger than average age (median 0.6 years). The most common functional disturbance was reduced lung or respiratory compliance with reduced lung volumes. Patients with and without lung involvement showed a similar pattern of involvement of other organs, with skin and bone most commonly affected. Of the 45 children with multisystem disease, 38 (84%) survived 2 to 7 years after diagnosis; there was a similar proportion of deaths in children with and without lung involvement. It is concluded that lung involvement occurs in nearly half of young children with multisystem Langerhans' cell histiocytosis but does not adversely affect outcome.
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Dermacentor variabilis, Rhipicephalus sanguineus, Amblyomma americanum, and Ixodes scapularis ticks were investigated for their ability to transmit Potomac horse fever. Larval and nymphal ticks were exposed to Ehrlichia risticii by feeding on mice inoculated with the organism. Molted exposed ticks were then allowed to feed on susceptible ponies or mice. No evidence of transmission, either clinically or by detection of antibodies to E. risticii in mice or ponies, was observed for any tick species examined.
The effect of physical and microbiological factors on food container leakage was investigated in a container leakage model system (CLMS). The leakage of Acinetobacter calcoaceticus, Staphylococcus sp., Pseudomonas sp., Bacillus sp., a coryneform, Staph. aureus, and two biotest organisms (Enterobacter cloacae NC1B 8151 and Ent. aerogenes MB31) was studied. The rate of bacterial leakage (log10 cells/channel/s) was greater in the presence of a partial vacuum of 51-305 mm Hg than at atmospheric pressure. Fluid flow (ml) through leakage channels was increased by the application of vacuum. Leakage varied with vacuum, bacterial morphology, cell concentration, leakage channel size (0.78-120 micron 2) and channel shape (straight or convoluted). The number of leaked cells was not proportional to vacuum or channel size. The effect of channel shape varied with bacterial species. Increased container medium viscosity decreased bacterial leakage. Fluid flow through leakage channels was generally reduced by the most viscous solution. Cells from biofilms and monolayers of Ac. calcoaceticus or Staph. aureus attached to nylon (Hyfax) or stainless steel surfaces underwent leakage. Mixed bacterial populations had characteristic leakage rates against vacuum different from the leakage pattern of individual species in the population. The composition of the leaked population was different from the original inoculum. The results indicated that container leakage is a complex process involving a range of interdependent factors.
A model system to study food container leakage was developed. The model system allows the independent investigation of the effect of physical factors such as vacuum and contents viscosity, and microbial factors on the leakage process. The design, construction and operation of the container leakage model system is described.
Elevated levels of human chorionic gonadotrophin are associated with primary testicular tumours and usually indicate the presence of trophoblastic elements. Human chorionic gonadotrophin can also be secreted by extragonadal tumours which may metastasize to the testes. A patient is described presenting with a testicular tumour secreting human chorionic gonadotrophin which later proved to be a metastasis from a pancreatic adenocarcinoma. Up to 70% of malignant pancreatic tumours can secrete human chorionic gonadotrophin.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most commonly used and therapeutically effective groups of drugs in the Western world. However, gastrointestinal problems constitute all too frequently reported unwanted effects of NSAIDs; their effects on the gastric (and intestinal) mucosa are, therefore, well documented. A review of the evidence suggests that NSAID-induced gastric damage occurs as a result of a dual insult, by NSAID-mediated direct (and indirect) acidic damage followed almost simultaneously by the deleterious (systemic) effect of prostaglandin inhibition. A number of strategies have been used in the management of NSAID-induced gastric damage; however, not all have been entirely successful. Nonetheless, a number of approaches have met with a considerable amount of success, including direct gastroprotection, enhancement of mucosal defence mechanisms and, perhaps most encouragingly, the development of newer NSAIDs which display not only considerable clinical efficacy but a reduced gastrointestinal adverse event profile.
A survey of schistosomiasis mansoni infection was conducted in an area of northwestern Ethiopia which has been targeted for an irrigation project. The proximity of settlements to water-bodies infested with Biomphalaria pfeifferi, and used extensively for bathing and domestic purposes, indicated that the potential for transmission is high. Snails shedding S. mansoni cercariae were found in two localities. Stool specimens from a total of 7517 persons were examined, including specimens from 4915 children age 7-14 years in 29 localities, as well as from the total population of four of the more heavily infected localities. The 10-14 year age group had the highest transmission potential, in terms of prevalence (overall 25%), intensity of infection, and absolute numbers of infected individuals, suggesting that screening and chemotherapy would be most cost-effective in that age group.
A serological study of antibodies to Ehrlichia risticii was carried out on 10 species of wild and domestic mammals found on or near 21 horse farms in an area of the USA in which Potomac horse fever is endemic. No antibodies were found in 133 peridomestic rodents (Norway rats and house mice), nor in 108 wild rodents (white-footed mice and meadow voles) captured on farms. Three of the six domestic animal species examined, cats, pigs and a goat, showed serological evidence of exposure to E risticii. Seropositive animals were detected on three of the 21 premises. The eight seropositive cats (of 48 cats tested) were on two farms, and the three seropositive pigs (of 14 tested) were all on one farm which lay some 3 km from where the one seropositive goat (of three tested) was found. None of the 79 dogs, 75 cattle and seven sheep tested had antibodies to E risticii. The significance of these findings is discussed in the light of current understanding of the transmission of Potomac horse fever and of the epidemiology of other related ehrlichial diseases.
The polymers involved in the adhesion of Pseudomonas fluorescens H2S to solid surfaces were investigated to determine whether differences between cell surface adhesives and biofilm matrix polymers could be detected. Two optical techniques, i.e., interference reflection microscopy (IRM) and light section microscopy (LSM), were used to compare the responses of the two types of polymer to treatment with electrolytes, dimethyl sulfoxide (DMSO), and Tween 20. To evaluate initial adhesive polymers, P. fluorescens H2S cells were allowed to attach to glass cover slip surfaces and were immediately examined with IRM, and their response to chemical solutions was tested. With IRM, changes in cell-substratum separation distance between 0 and ca. 100 nm are detectable as changes in relative light intensity of the image; a contraction of the polymer would be detected as a darkening of the image, whereas expansion would appear as image brightening. To evaluate the intercellular polymer matrix in biofilms, 3-day-old biofilms were exposed to similar solutions, and the resultant change in biofilm thickness was measured with LSM, which measures film thicknesses between 10 and 1,000 microns. The initial adhesive and biofilm polymers were similar in that both appeared to contract when treated with electrolytes and to expand when treated with Tween 20. However, with DMSO treatment, the initial adhesive polymer appeared to contract, whereas there was no change in thickness of the biofilm polymer. These results indicate that both polymers bear acidic groups and thus act electrostatically with cations and are able to enter into hydrophobic interactions.(ABSTRACT TRUNCATED AT 250 WORDS)
Sites of close contact between gliding Cytophaga sp. strain U67 cells and glass were examined by interference reflection microscopy. Site patterns changed during translocation and moved relative to the substratum, in contrast to previous interference reflection microscopy observations of fibroblast and amoeboid motility. Sinistral rotation around the long axis of the cell was coupled with gliding, except when curved cells traversed curvilinear pathways. Close contact was temporary, since cells flipped up off the substratum on one pole, pivoted, or were displaced laterally in collisions. Other members of the order Cytophagales and Myxococcus sp. demonstrated similar patterns of close association with substrata.
We analyzed the metacarpophalangeal pattern profile (MCPP) on 18 male individuals from 16 families with fragile X--fra (X), or Martin-Bell--syndrome and calculated a mean syndrome profile. Fourteen of 18 individuals with fra (X) syndrome had significant positive correlations which indicated clinical homogeneity. Discriminant analysis of individuals with fra (X) syndrome compared with a sample of normal individuals produced a correct classification rate of 88% based on a function of 3 MCPP variables that may provide a useful tool in screening individuals for the fra (X) syndrome. Discriminant and correlation analyses of individuals with Sotos sequence and individuals with fra (X) syndrome did not identify MCPP similarities. Therefore, there was no MCPP evidence in our study of patients with Sotos sequence and fra (X) chromosome expression.
The influence of Na+, Ca2+, La3+, and Fe3+ on the adhesion of Pseudomonas fluorescens H2 and H2S was investigated with interference reflection microscopy (IRM). IRM is a light microscopy technique which allows (i) visualization of the adhesive sites of living bacteria as they attach to a glass cover slip surface and (ii) evaluation of the bacterium-glass surface separation distance within a range of 0 to ca. 100 nm. The addition of each cation caused changes in IRM images consistent with a decrease in the separation distance, and minimum effective concentrations were as follows: Na+, 1 mM; Ca2+, 1 mM; La3+, 50 microM; and Fe3+, 50 microM. With strain H2, the effects of Na+, Ca2+, and La3+ were fully reversible in that the separation distance increased again when the electrolyte was replaced with distilled water. However, with strain H2S, a spontaneous mutant of H2 with increased attachment ability, only the effect of Na+ was fully reversible, and the effects of Ca2+ and La3+ were only partially reversible or irreversible. The effect of Fe3+ was irreversible with both strains, but this may be related not only to the electrolytic nature of Fe3+ but also to the decrease in solution pH to 3.5 caused by its addition. It is proposed that the electrolytes caused a decrease in separation distance by neutralizing negative charges on bacterial surface polymers and that the different effects obtained with the two strains are related to their different adhesion abilities.