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Biomedical subjects

I Simmons

Publications and source records attributed to I Simmons.

10 recordsLinked to original sources
PubMed1998

Optic nerve breast metastasis mimicking meningioma.

PURPOSE: We report on an optic nerve breast metastasis masquerading initially as a central retinal vein occlusion and later as an optic nerve meningioma. METHODS: A 60-year-old female presented with a left central retinal vein occlusion (CRVO). She represented 7 months later with left upper ptosis, proptosis and painful rubeotic glaucoma Computed tomography (CT) and magnetic resonance imaging suggested an optic nerve meningioma. On referral to the regional orbital unit a mild left external ophthalmoplegia was noted and, in view of previous right mastectomy and chemotherapy 3 years earlier, the left optic nerve was biopsied simultaneously with left enucleation of her painful eye. RESULTS: Histopathology showed infiltration of the optic nerve and meningeal sheath spreading into the subretinal space and vitreous by malignant epithelial cells, consistent with breast origin. Further CT imaging and bone scans revealed no other metastases. Single field left orbit radiotherapy of 20 Gy was given in five fractions and Arimidex (Zeneca Pharmaceuticals, Cheshire, England) was commenced with the cessation of tamoxifen. The patient was also given an ocular prosthesis. Sadly, she lost vision in her other eye due to retrograde malignant invasion of her optic chiasm and died 6 weeks later. CONCLUSIONS: Orbital and choroidal metastases are relatively common but isolated optic nerve metastases are extremely rare. Progressive infiltration of the nerve is likely to enhance CRVO ischaemia and resultant rubeotic glaucoma. In the diagnosis of CRVO, proptosis or external ophthalmoplegia, the presence of pre-existing malignant disease should raise concerns, as delay in diagnosis may affect outcome, particularly if the metastases are sensitive to pharmacological therapy.

Blepharoptosis↗
PubMed1992

The relationship between Trichuris trichiura transmission intensity and the age-profiles of parasite-specific antibody isotypes in two endemic communities.

The present study compares parasite-specific antibody responses in two Caribbean communities with high and low levels of Trichuris trichiura transmission. The age-dependency of antibody levels suggest that IgG1 and IgG2 levels relate to the current intensity of infection (as assessed by density of eggs in stool (e.p.g.) and reflect the age-intensity profile at the population level. IgG4, IgE and IgA levels persist into early adulthood and the subsequent decline is gradual. In the low transmission area, lower infection levels are reflected in lower parasite-specific antibody levels (of all isotypes) in the community as a whole. Despite a significantly greater past experience of infection in the high transmission area, antibody levels are not maintained at significantly higher levels throughout adulthood. The production of IgA appears to require a threshold for triggering, and a vigorous IgA response is maintained into early adulthood only in the high transmission village where peak intensity is greatest and the age-convexity of intensity is most marked. Experimental and theoretical studies focusing on the dynamic nature of host-helminth interactions in hosts exposed to high and low infection levels, and the putative role of acquired immunity, are discussed in relation to the data presented.

Adolescent↗
PubMed1991

Age-dependency of infection status and serum antibody levels in human whipworm (Trichuris trichiura) infection.

This study examines the age-dependency of the relationships between human infection with whipworm (Trichuris trichiura) and parasite-specific antibody level measured by ELISA against an extract of adult worms after preincubation of the sera with Ascaris lumbricoides adult worm extract. The convex age-profile of parasite infection intensity is shown to be mirrored by an age-dependent change in age-class mean levels of IgG (all subclasses except IgG3), IgA, IgM and IgE. Mean antibody levels rise with increasing acquisition of infection in childhood and decline as the intensity of infection falls in adulthood. Immunoblot analysis of selected sera from different age-classes indicates that antigen recognition is similarly dependent on infection intensity. In individual children, antibody levels correlate positively with acquisition of infection, consistent with a simple model of antigen dosage specifying the magnitude of the humoral immune response. In adults, IgG4 correlates positively and IgA negatively with intensity of infection, suggesting involvement of these isotypes in functional roles of immune blockade or effector mechanisms, respectively.

Adolescent↗
PubMed1989

Seroepidemiological study of the transmission of the mumps virus in St. Lucia, West Indies.

A seroepidemiological study of the prevalence of mumps virus specific antibodies reveals a pattern of endemic persistence on the island of St Lucia in the West Indies. In the unvaccinated population the proportion seropositive rose rapidly in the child age classes to attain a stable plateau close to unity in value in the teenage and adult age groups. The average age at infection was estimated to be between 3 and 4 years of age and the average duration of detectable levels of maternally derived antibodies was approximately 3 months. Analyses based on mathematical models of the transmission dynamics of the virus suggest that in excess of 75% of each cohort of 1- to 2-year-old children must be effectively immunized to eliminate mumps virus transmission. A mumps radial haemolysis test, developed for quantitative measurements of antibody, is discussed.

Adolescent↗
PubMed1988

Effect of age and initial infection intensity on the rate of reinfection with Trichuris trichiura after treatment.

The study examines the rate of re-acquisition of Trichuris trichiura infection after treatment in two populations, one of mixed age and the other of children with known pre-intervention infection intensity. A population living in a Caribbean village was treated with mebendazole and the rate of reacquisition of infection of four age classes (2-4, 5-10, 11-30, 30+ years) monitored over a 20-month period. The reinfection rate was higher in the child age-classes indicating either that children are more exposed to infection or that adults slowly develop a partially effective acquired immunity. A cohort of children (mean age 4.5 years) was separated into 3 intensity categories on the basis of expelled worm burdens and their rate of reacquisition of infection monitored over a 12-month period. The rate of reinfection was directly and positively associated with initial infection status. This may indicate that children with low intensity infections are consistently less exposed to infection or that they have effective immune responses. The latter conclusion, however, would imply that they had acquired this immunity early in life, and so appears to contradict the suggestion that resistance is only slowly acquired by adults. Reconciling these two conclusions may require more sophisticated immunological models than have been suggested previously for geohelminthiases.

Adolescent↗
PubMed1987

Epidemiology and population dynamics of Ascaris lumbricoides and Trichuris trichiura infection in the same community.

The gastrointestinal helminth infection status of an age-stratified sample from a single Caribbean community was assessed using anthelmintic expulsion techniques. The same sample was re-assessed in a similar manner after a 17 month period of re-infection. The age-prevalence profile of Ascaris lumbricoides was convex while that of Trichuris trichiura was asymptotic. The age-intensity profiles of both species were convex. These differing patterns are attributed to differences in the absolute worm burdens of the 2 species. The frequency distributions of infection intensity were similar for both species, and largely independent of host age. The basic reproductive rate of A. lumbricoides (Ro = 1-1.8) was similar to that recorded elsewhere and much lower than that of T. trichiura (Ro = 4-6), implying that the latter is intrinsically more resistant to control. Individual hosts were predisposed to high (or low) intensity infection with either species, although predisposition to both species simultaneously was not conclusively demonstrated. Further studies are required to determine the cause of these observations.

Adolescent↗
PubMed1987

Predisposition to Trichuris trichiura infection in humans.

The study examines the distribution of Trichuris trichiura infection in a village community in St Lucia, West Indies. The infection intensity of the same age-stratified population was assessed (by drug expelled worm burden and faecal egg count) at the initiation of the study, and after 17 months of reinfection following treatment. The frequency distribution of worm numbers per person was similar at both periods of sampling. There was a significant correlation between the initial infection intensity of an individual, and the intensity acquired by the same individual following the 17 month period of reinfection. This relationship was observed in a broad range of host age classes. The study provides firm evidence that individuals are predisposed to heavy (or light) T. trichiura infection.

Adolescent↗