Tag: twin studies

Unique genetic and environmental determinants of prolonged fatigue: a twin study

Abstract:

BACKGROUND: Prolonged fatigue syndromes have been proposed as prevalent and disabling forms of distress that occur independently of conventional notions of anxiety and depression.

METHODS: To investigate the genetic and environmental antecedents of common forms of psychological and somatic distress, we measured fatigue, anxiety, depression and psychological distress in 1004 normal adult twin pairs (533 monozygotic (MZ), 471 dizygotic (DZ)) over 50 years of age.

RESULTS: Familial aggregation of psychological distress, anxiety and fatigue appeared to be due largely to additive genetic factors (MZ:DZ ratios of 2.12-2.69). The phenotypic correlations between the psychological measures (distress, anxiety and depression) were moderate (0.67-0.79) and higher than that between fatigue and psychological distress (0.38). Multivariate genetic modelling revealed a common genetic factor contributing to the development of all the observed phenotypes (though most strongly for the psychological forms), a second independent genetic factor also influenced anxiety and depression and a third independent genetic factor made a major contribution to fatigue alone. In total, 44% (95% CI 25-60%) of the genetic variance for fatigue was not shared by the other forms of distress. Similarly, the environmental factor determining psychological distress made negligible contributions to fatigue, which was underpinned largely by its own independent environmental factor.

CONCLUSION: This study supports the aetiological independence of prolonged fatigue and, therefore, argues strongly for its inclusion in classification systems in psychiatry.

 

Source: Hickie I, Kirk K, Martin N. Unique genetic and environmental determinants of prolonged fatigue: a twin study. Psychol Med. 1999 Mar;29(2):259-68. http://www.ncbi.nlm.nih.gov/pubmed/10218917

 

MELISA-an in vitro tool for the study of metal allergy

Abstract:

The sensitizing properties of metals widely used in medical and dental care have been studied with the help of an optimized lymphocyte proliferative assay, MELISA. MELISA (memory lymphocyte immuno-stimulation assay) was originally developed for the screening of allergenic epitopes of drugs and other chemicals of low molecular weight, but has recently been adapted for the study of metal-induced sensitization.

The patients studied suffered from various oral mucosal problems which were suspected to be caused by the release of metal ions from dental restorations. They were also troubled by chronic fatigue persisting over many years. One patient was also occupationally exposed to metals while working in a dental practice. Healthy subjects without any discomfort due to metal devices served as controls. In addition to metals used in dentistry, lymphocyte responses to organic mercurials used widely as preservatives in vaccines, eye/nose drops and contact lense fluids were studied.

The results indicated that mercurials, as well as other metals such as gold or palladium, induce strong lymphocyte proliferative responses in patients with oral or systemic symptoms, but not in similarly exposed unaffected subjects.

The results of MELISA performed with a pair of identical twins with chronic fatigue syndrome (CFS) indicated that metal-specific responses may be dependent on the genetics of the patient. Thus, many metals that are today accepted for use in medicine and dentistry carry a definite sensitizing risk for certain genetically predisposed individuals. Therefore, the use of these metals should be limited in the future.

 

Source: Stejskal VD, Cederbrant K, Lindvall A, Forsbeck M. MELISA-an in vitro tool for the study of metal allergy. Toxicol In Vitro. 1994 Oct;8(5):991-1000. http://www.ncbi.nlm.nih.gov/pubmed/20693060