On the importance of fatty acid composition of membranes for aging

The membrane pacemaker theory of aging is an extension of the oxidative stress theory of aging. It emphasises variation in the fatty acid composition of membranes as an important influence on lipid peroxidation and consequently on the rate of aging and determination of lifespan. The products of lipid peroxidation are reactive molecules and thus potent damagers of other cellular molecules. It is suggested that the feedback effects of these peroxidation products on the oxidative stress experienced by cells is an important part of the aging process. The large variation in the chemical susceptibility of individual fatty acids to peroxidation coupled with the known differences in membrane composition between species can explain the different lifespans of species, especially the difference between mammals and birds as well as the body-size-related variation in lifespan within mammals and birds. Lifespan extension by calorie-restriction can also be explained by changes in membrane fatty acid composition which result in membranes more resistant to peroxidation. It is suggested that lifespan extension by reduced insulin/IGF signalling may also be mediated by changes in membrane fatty acid composition.     

Cytokine gene polymorphisms and atopic disease in two European cohorts. (ECRHS-Basel and SAPALDIA)

Background

Avoidance of allergens is still recommended as the first and best way to prevent allergic illnesses and their comorbid diseases. Despite a variety of attempts there has been very limited success in the area of environmental control of allergic disease. Our objective was to identify a non-invasive, non-pharmacological method to reduce indoor allergen loads in atopic persons' homes and public environments. We employed a novel in vivo approach to examine the possibility of using aluminum sulfate to control environmental allergens.

Methods

Fifty skin test reactive patients were simultaneously skin tested with conventional test materials and the actions of the protein/glycoprotein modifier, aluminum sulfate. Common allergens, dog, cat, dust mite, Alternaria, and cockroach were used in the study.

Results

Skin test reactivity was significantly reduced by the modifier aluminum sulfate. Our studies demonstrate that the effects of histamine were not affected by the presence of aluminum sulfate. In fact, skin test reactivity was reduced independent of whether aluminum sulfate was present in the allergen test material or removed prior to testing, indicating that the allergens had in some way been inactivated.

Conclusion

Aluminum sulfate was found to reduce the in vivo allergic reaction cascade induced by skin testing with common allergens. The exact mechanism is not clear but appears to involve the alteration of IgE-binding epitopes on the allergen. Our results indicate that it may be possible to diminish the allergenicity of an environment by application of the active agent aluminum sulfate, thus producing environmental control without complete removal of the allergen.     

Unusual growth pattern in the Frasnian alveolitids (Tabulata) from the Holy Cross Mountains (Poland)

Abstract: Growth periodicity is a phenomenon occurring in fossil and modern corals. The most apparent feature is growth banding, and environmental changes are broadly accepted as controls on this phenomenon. If environment controls the growth, then all corallites within a colony should repeat the same growth pattern, as individuals are clones and must have shared the same environment. A study on several species of Alveolitidae (Anthozoa, Tabulata) from the Late Devonian (Early Frasnian) of the Holy Cross Mountains (Poland) shows that the growth pattern varies between neighbouring individuals within the same corallum. This contradicts observations of closely related Favositida as demonstrated on Pachyfavosites sp. from the Givetian of Avesnois, France, where neighbouring individuals repeat the same pattern. Therefore, environmental control on growth rhythm in Alveolitidae can be excluded; the causes of differences between individuals remain unknown.     

Thyroid function in a lizard, a tortoise and a crocodile, compared with mammals

1. Thyroid activity was examined in the lizard, Trachydosaurus rugosus, the tortoise Chelodina longicollis and the crocodile, Crocodylus johnstoni, acclimated to 20-22 degrees C and 30-32 degrees C. Thyroidal uptake and release of 125I, plasma concentrations of T3 and T4 were measured as was resting oxygen consumption (at 30 degrees C) before and after both thyroidectomy and thyroxine injections. 2. All three species showed 125I uptake at both temperatures and showed no thyroidal release of 125I at 20-22 degrees C but exhibited thyroidal release of 125I (and presumably hormone secretion) at 30-32 degrees C. 3. Plasma concentrations of thyroxine ranged from 0.55 nM to 3.24 nM and triiodothyronine from 0.14 nM to 0.51 nM. 4. Neither thyroidectomy nor thyroxine injections had any effect on metabolic rate in 20-22 degrees C acclimated lizards. Thyroidectomy resulted in a significant decrease in metabolic rate in 30-32 degrees C acclimated lizards and tortoises and thyroxine injections resulted in significant increases in metabolism in 30-32 degrees C acclimated lizards, tortoises and crocodiles. 5. A comparison of thyroid parameters in reptiles and mammals concluded that although the reptilian thyroid is active at high temperatures it is still considerably less active than it is in mammals.     

Effect of Age and Menopausal Status on Estimates of Oestrogen Binding by Human Malignant Breast Tumours

The uptake of oestradiol by human breast-tumour tissue estimated by in-vivo and in-vitro techniques has been examined in relation to patients'' ages and menopausal status. Results from in-vivo studies showed no convincing correlations, while in-vitro results were significantly correlated with menopausal status. There was a significant correlation between results obtained by the two techniques.     

Membranes as possible pacemakers of metabolism.

Basal metabolic rate (BMR) varies dramatically among vertebrate species, both (i) being several fold higher in the endothermic mammals and birds compared to the ectothermic reptiles, amphibians and fish, and (ii) being much greater, on a body mass basis, in small vertebrates compared to large vertebrates. These differences in whole animal BMR are also manifest at the cellular level with substantial contributions to basal metabolic activity from the maintenance of various trans-membrane gradients. The percentage contribution of various processes to basal metabolism is remarkably consistent between different vertebrates and when BMR varies, the components of metabolic activity vary in relative unison. Membrane composition also varies between vertebrates and the degree of polyunsaturation of membrane phospholipids is correlated with cellular metabolic activity. In general, the tissue phospholipids and thus membrane bilayers of endotherms are more polyunsaturated than those from similar-sized ectotherms. In mammals membrane polyunsaturation is allometrically related to body mass. We suggest that membranes can act as pacemakers for overall metabolic activity. We propose that such membrane polyunsaturation increases the molecular activity of many membrane-bound proteins and consequently some specific membrane leak-pump cycles and cellular metabolic activity. We hypothesize a possible mechanistic basis for this effect that is based on a greater transfer of energy during intermolecular collisions of membrane proteins with the unsaturated two carbon units (C=C) of polyunsaturates compared to the single carbon units of saturated acyl chains, as well as the more even distribution of such units throughout the depth of the bilayer when membranes contain polyunsaturated acyl chains compared to monounsaturated ones. The proposed pacemaker role of differences in membrane bilayer composition is briefly discussed with respect to the brain (and sensory cells), evolution of mammalian endothermic metabolism, and its clinical implications for humans.