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Biomedical subjects

J R Armstrong

Publications and source records attributed to J R Armstrong.

At least 19 recordsLinked to original sources
PubMed1995

Ontogeny of the skin and the transition from scar-free to scarring phenotype during wound healing in the pouch young of a marsupial, Monodelphis domestica.

The marsupial Monodelphis domestica provides a versatile model for the study of "fetal" wound healing. The pouch young of this species have been used to perform a systematic histological study of wound healing and skin development throughout pouch life; from Pouch Day 0 to Pouch Day 30 with comparisons drawn against adults. We have demonstrated that pouch young heal without macroscopic scars if wounded before Pouch Day 9 and that a transition into a scarring healing phenotype occurs around the ninth pouch day. The inflammatory reaction of wounds and aspects of skin differentiation such as dermal collagen organisation, adipose layer development, hair follicle growth, and epithelial maturation have been documented using simple ranking scales to highlight trends through pouch life. Inflammation was noted to become prominent after Pouch Day 9. There was also a general temporal correlation between the other aspects of differentiation and the transition into a scarring phenotype. It is concluded that although fetal wounds may have different cytokine profiles due to the differences of inflammatory reaction compared to adults, other aspects of skin development play a role in determining the healing phenotype.

Aging↗
PubMed1992

Childhood deaths in Africa: uses and limitations of verbal autopsies.

The verbal autopsy (VA) is an epidemiological tool that is widely used to ascribe causes of death by interviewing bereaved relatives of children who were not under medical supervision at the time of death. This technique was assessed by comparison with a prospective survey of 303 childhood deaths at a district hospital in Kenya where medically confirmed diagnoses were available. Common causes of death were detected by VA with specificities greater than 80%. Sensitivity of the VA technique was greater than 75% for measles, neonatal tetanus, malnutrition, and trauma-related deaths; however, malaria, anaemia, acute respiratory-tract infection, gastroenteritis, and meningitis were detected with sensitivities of less than 50%. There may have been unwarranted optimism in the ability of VAs to detect some of the major causes of death, such as malaria, in African children. VA used in malaria-specific intervention trials should be interpreted with caution and only in the light of known sensitivities and specificities.

Cause of Death↗
PubMed1991

The effect of insecticide-treated bed nets on mortality of Gambian children.

Insecticide treatment of bed nets ("mosquito nets") may be a cheap and acceptable method of reducing the morbidity and mortality caused by malaria. In a rural area of The Gambia, bed nets in villages participating in a primary health-care (PHC) scheme were treated with permethrin at the beginning of the malaria transmission season. Additionally, children aged 6 months to 5 years were randomised to receive weekly either chemoprophylaxis with maloprim or a placebo throughout the malaria transmission season. We measured mortality in children in PHC villages before and after the interventions described, and compared this with mortality in villages where no interventions occurred (non-PHC villages). About 92% of children in PHC villages slept under insecticide-treated bed nets. In the year before intervention, mortality in children aged 1-4 years was lower in non-PHC villages. After intervention, the overall mortality and mortality attributable to malaria of children aged 1-4 in the intervention villages was 37% and 30%, respectively, of that in the non-PHC villages. Among children who slept under treated nets, we found no evidence of an additional benefit of chemoprophylaxis in preventing deaths. Insecticide-treated bed nets are simple to introduce and can reduce mortality from malaria.

Antimalarials↗
PubMed1991

Indoor air pollution exposure and lower respiratory infections in young Gambian children.

In a rural population-based cohort study of approximately 500 Gambian children under five years old followed for one year, incidence of acute lower respiratory infections (ALR) was related to various risk factors including parental smoking and regular carriage on the mother's back while cooking, a proxy measure for exposure to smoke from cooking fires. Two statistical analyses using a 'child-weeks at risk' approach were carried out, including and excluding multiple disease episodes in the same child. Weekly surveillance for ALRI found 75 episodes in 62 children. Stratified analyses using both approaches suggested father's smoking, and, for girls only, carriage on the mother's back while cooking and being part of a polygamous family were the main risk factors associated with infection: when multiple episodes occurring in the same child were excluded, not having a health card was an additional risk factor in children over a year old. Multiple logistic regression modelling of data from both approaches, including each of these risk factors and sex, age, village and season, suggested father's smoking, carriage on the mother's back while cooking and being part of a polygamous family increase risk of ALRI, the latter two for girls only. The analysis excluding multiple episodes in the same child also suggested that not having a health card is a risk factor for children aged 1-5 years. The difficulties in interpreting these findings are discussed.

Acute Disease↗
PubMed1991

Experimental hut trials of bednets impregnated with synthetic pyrethroid or organophosphate insecticide for mosquito control in The Gambia.

1. Nylon bednets impregnated with different insecticides were evaluated in 1988 against wild adult mosquito populations, mostly Mansonia africana (Theobald) and Anopheles gambiae Giles sensu lato, entering experimental verandah-trap huts in The Gambia. Each bednet had six 10 x 10 cm holes made in the walls to simulate torn conditions and permit female mosquitoes to enter and feed on sleepers. 2. Individual net treatments, determined by gas chromatography of net samples from before and after 12 weeks use of the bednets, were: permethrin 670 +/- 159 and 405 +/- 190 mg/m2 (40% loss), cypermethrin 37 +/- 8 and 16 +/- 9 mg/m2 (57% loss), deltamethrin 10 +/- 7 and 10 +/- 8 mg/m2 (no loss), lambda-cyhalothrin 2.6 +/- 0.9 and 1.6 +/- 0.5 mg/m2 (38% loss), pirimiphos-methyl 4017 +/- 117 and 1160 +/- 319 mg/m2 (71% loss). 3. Washing three times in the traditional manner with local cow-fat soap reduced the initial dosages by about 85% of cypermethrin and lambda-cyhalothrin, 99.8% of pirimiphos-methyl and left no detectable residues of deltamethrin or permethrin. 4. The unwashed permethrin-treated bednet reduced the number of mosquitoes entering a hut by 60% of An.gambiae s.l. and 68% of Mansonia spp. This deterrency was less pronounced with the other insecticides and was lost by washing the bednets. 5. Each insecticide, especially lambda-cyhalothrin and pirimiphosmethyl, caused significant mortality rates of mosquitoes that entered huts with impregnated bednets, and prevented the majority of An. gambiae s.l. and Mansonia females from bloodfeeding. Washing completely removed the efficacy of deltamethrin and permethrin treated bednets, whereas nets treated with cypermethrin, lambda-cyhalothrin or pirimiphos-methyl remained significantly insecticidal after washing. 6. Aerial toxicity from the pirimiphos-methyl treated bednet killed 80% of An.gambiae s.l. confined overnight in the hut at the end of the trial, whereas the pyrethroid-treated bednets gave negligible mortality rates of mosquitoes. 7. Sleepers using the bednets had no medical symptoms significantly associated with any of the treatments. On the contrary, from 216 interviews, 4/10 complaints were associated with the use of untreated nets (P approximately 0.05), perhaps because sleepers were kept awake by mosquitoes and became more aware of any ailments. 8. It is concluded that permethrin tends mainly to deter mosquitoes from house-entry, enhancing personal protection, whereas the other insecticides kill higher proportions of the endophilic mosquitoes, which would give better community protection against malaria transmission.

Analysis of Variance↗
PubMed1991

Pyrethroid-treated bednet effects on mosquitoes of the Anopheles gambiae complex in The Gambia.

The response of Anopheles gambiae complex mosquitoes to men sleeping under insecticide-impregnated or untreated bednets in six verandah trap huts was studied during the dry season in The Gambia. With this type of hut it was possible to collect live and dead indoor-resting mosquitoes and estimate the number of wild mosquitoes which entered, bloodfed on man, and exited each night. Bednets were treated with emulsions targetted to leave deposits of 25 mg/m2 lambda-cyhalothrin, or 5, 50 or 500 mg/m2 permethrin, diluted from emulsifiable concentrates (EC), or a blank formulation similar to the EC except that the permethrin was omitted; the sixth net was left untreated. Nets and sleepers were rotated between huts on different nights, the design being based on a series of Latin squares and conducted double-blind. Permethrin-impregnated bednets deterred mosquitoes from entering the huts. The degree of deterrency was proportional to the dosage of permethrin. This effect was also caused by the blank formulation and therefore attributed to other components of the formulation, rather than to the permethrin itself. The net impregnated with 500 mg permethrin per square metre gave the best individual protection, reducing mosquito bloodfeeding by 91% compared with untreated nets. However, lambda-cyhalothrin was proportionately more insecticidal than permethrin at doses of equivalent deterrency. At this stage of research, it remains conjectural whether chemical deterrency or killing of malaria vectors is better for community protection.

Animals↗
PubMed1990

Antibody persistence in Gambian children after high-dose Edmonston-Zagreb measles vaccine.

Measles antibody concentrations in Gambian children immunised at 4 months of age with a high-dose Edmonston-Zagreb (EZ) measles vaccine or at 9 months with conventional Schwarz vaccine were measured 5 months after vaccination, and at 18 and 36 months of age. Schwarz vaccinees produced, on average, a 2.4-fold higher concentration of measles haemagglutinin inhibiting (HAI) antibody than EZ vaccinees, but at 36 months of age 82 of 93 (88%) EZ vaccinees and 83 of 87 (95%) Schwarz vaccinees had measles plaque-neutralising antibody concentrations above the assumed protective level of 200 mIU/ml (p greater than 0.1). HAI antibody concentrations 5 months after vaccination were inversely related to the presence of maternal antibody at vaccination, but above protective levels; at 18 and 36 months of age there was no relation to antibody concentration at vaccination, and decay of HAI antibody between 18 and 36 months of age was similar for EZ and Schwarz vaccinees.

Age Factors↗
PubMed1989

Permethrin-impregnated bednets reduce nuisance arthropods in Gambian houses.

The prevalence of bedbugs (Cimex hemipterus L.), chicken ticks (Argas persicus Oken) and headlice (Pediculus capitis De Geer) was surveyed in a rural area of The Gambia. At the beginning of the study 37.5% of children's beds were infested with bedbugs and 3.9% with chicken ticks, whilst the prevalence rate of pediculosis in children under 10 years old was 28.8%. Both bedbugs and headlice were clustered within compounds. Headlice prevalence increased with hair length and they were more common on girls than boys. Following this cross-sectional survey all bednets in the sixteen hamlets were either dipped in permethrin or a placebo. About 4 months later it was found that bedbugs and chicken ticks had disappeared from homes in which the bednets had been impregnated with permethrin. There was no reduction in hamlets with placebo-treated bednets. The rate of acquiring headlice between the two surveys was reduced by 91.1% in children who slept under insecticide-treated bednets compared with children with placebo-treated bednets. There were also significantly fewer day-flying and crawling insects, except earwigs, in homes of children who slept under insecticide-treated bednets compared with those with placebo-treated nets. These additional benefits of permethrin-treated bednets should contribute to their widespread acceptance and utilization by the community for personal protection.

Animals↗
PubMed1984

Haemophilus influenzae corneal ulcer in a therapeutic contact lens wearer.

Haemophilus influenzae is an unusual corneal pathogen and an unusual cause of corneal ulcers in Western society. In previous reports corneal complications from H. influenzae have been secondary to a conjunctivitis. The first case of a primary H. influenzae corneal ulcer as a complication of therapeutic contact lens wear is presented. Since other uncommon bacteria have been reported as causes of contact lens related corneal ulcers, the bacteriology of contact lens related corneal ulcers is reviewed. Ophthalmologists need to be aware that H. influenzae infections in adults are becoming more frequent.

Aged↗
PubMed1981

Eradication of tuberculosis from an extensively managed beef herd.

Eradication of tuberculosis from a herd of 5,000 head of beef cattle with a long history of infection was achieved in a 5-year period using the single caudal fold tuberculin test in conjunction with segregation of breeders of different ages and selective slaughter of problem groups. The major problem which had to be overcome to achieve eradication was the occurrence of anergic tuberculous animals. All animals in the group were slaughtered when it was apparent testing was not successful. Testing was very effective in eliminating TB from cattle under the age of two years. Incomplete musters and breakdown of segregation caused reinfection of clean groups in the early stages.

Animals↗