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Biomedical subjects

J L Sheridan

Publications and source records attributed to J L Sheridan.

9 recordsLinked to original sources
PubMed1981

The etiology of multiple sclerosis: temporal-spatial clustering indicating two environmental exposures before onset.

Studies in the Orkney and Shetland Islands have demonstrated the highest rates of multiple sclerosis (MS) recorded. Accumulated evidence suggests that an environmental factor is paramount in etiology. The role of an environmental exposure (infectious or toxic) is confirmed in this study by the demonstration in Orkney of clustering of cases in time and space. Lifetime data showed temporal-spatial clustering of MS patients (1) at least 21 years prior to onset, and (2) just prior to onset. Each of the two time clusters occurred on three separate islands. No clustering was seen at birth, by chronological age, or by schooling. Clustering was not demonstrated in Shetland. Previous efforts to demonstrate clustering may have failed because of lack of specificity of the data or inappropriate methodology. These data indicate that not one but two environmental factors play a role in the etiology of MS, representing exposures to two different environmental insults, or exposure twice to the same insult, prior to onset of MS.

Epidemiologic Methods↗
PubMed1980

Multiple sclerosis in the Orkney and Shetland Islands. I: Epidemiology, clinical factors, and methodology.

An epidemiological and clinical study of multiple sclerosis (MS) in the Orkney and Shetland Islands showed that the prevalence rate of the disease is the highest in the world (309 and 184/100 000, respectively). The clinical entity, MS, is similar to that found in other parts of the world, except that optic neuritis not followed by MS is rare. Analysis of death certificates indicated that MS has probably occurred at the same rate in these islands for nearly a century. Although the incidence of MS is high, the incidence rate has remained constant over time. A rapidly increasing prevalence of MS has occurred in Orkney, with a more modest increase in Shetland, over the past 20 years, which is largely due to an increase in survival. Demographic factors, case ascertainment, and emigration have contributed little to the increasing prevalence of MS in these islands.

Age Factors↗
PubMed1980

Multiple sclerosis in the Orkney and Shetland Islands. II: The search for an exogenous aetiology.

In Orkney and Shetland, a survey of lifetime events was undertaken in multiple sclerosis patients and two control groups to define shared exposure to an exogenous agent or environmental insult. Analyses of demographic factors, diet, social class and occupation, housing and environment, animal exposure, schooling, travel, infectious disease, and medical history disclosed a remarkable similarity in responses between patients and controls for a majority of questions. However, differences were noted for sanitation, place of residence at onset, and animal exposure. The data give additional support for an exogenous aetiology of multiple sclerosis.

Animal Population Groups↗
PubMed1980

Multiple sclerosis in the Orkney and Shetland Islands. III: Histocompatibility determinants.

Histocompatibility testing was performed in 48 multiple sclerosis patients and two carefully matched control groups in Orkney Islands, an area of high multiple sclerosis prevalence. The frequency of HLA-A3, HLA-B7, and DW2 was comparable in patients and controls. However, HLA-B7 was significantly more common in female patients compared with male patients. A B-cell alloantigen (B-cell 4) was also as frequent in patients as among controls. Strong linkage between HLA-B7, DW2 and B-cell 4 occurred in controls, but not patients; the linkage was particularly striking in female controls. These data are not consistent with theories that relate certain of the histocompatibility antigens to the aetiology of multiple sclerosis.

B-Lymphocytes↗
PubMed1980

Multiple sclerosis in the Orkney and Shetland Islands. IV: Viral antibody titres and viral infections.

A controlled serologic survey of antibody titres to 17 viruses was undertaken in multiple sclerosis patients in the Orkney and Shetland Islands. No consistent pattern of elevated antibody titre levels or the presence of antibody was noted in patients compared with two control groups. Because of the isolation of these islands, the mean age at acquisition of common childhood infections, including measles, was considerably older than that of inhabitants of Europe and the United States of America. The age of occurrence of varicella was consistently younger in patients than in controls. Of note is the fact that six patients had measles after the onset of MS. This study failed to incriminate any of the viruses tested in the aetiology of MS.

Age Factors↗
PubMed1980

Multiple sclerosis in the Orkney and Shetland Islands. V: The effect on viral titres of histocompatibility determinants.

HLA phenotypes were correlated with serum antibody titres to eight viruses in patients with multiple sclerosis and two matched control groups in the Orkney Islands. In patients, no specific HLA antigen was associated wtih increased or decreased viral titres. However, HLA-B7 was significantly correlated with higher measles titres in healthy controls. Furthermore, controls who had the HLA haplotypes, B7, DW2 ad B-cell 4, demonstrated significantly higher antibody titres to measles and rubella than controls without these determinants (P less than 0.005). To determine the effect of age, sex, and other variables upon viral titres, regression analysis was undertaken. A significant proportion of measles titre variance in patients was explained by sex and clinical factors. Among normal controls, HLA determinants explained a significant amount of measles and rubella titre variance. These data suggest that viral titres in normal individuals are influenced by certain HLA antigens and give indirect evidence that another, as yet undefined, determinant in the histocompatibility complex governs the immune response.

Antibodies, Viral↗