Successful treatment of auditory perceptual disorder in individuals with Friedreich ataxia.

Friedreich ataxia (FRDA) is a neurodegenerative disease affecting motor and sensory systems. This study aimed to investigate the presence and perceptual consequences of auditory neuropathy (AN) in affected individuals and examine the use of personal-FM systems to ameliorate the resulting communication difficulties. Ten individuals with FRDA underwent a battery of auditory function tests and their results were compared with a cohort of matched controls. Friedreich ataxia subjects were then fit with personal FM-listening devices and evaluated over a 6 week period. Basic auditory processing was affected with each FRDA individual showing poorer temporal processing and figure/ground discrimination than their matched control. Speech perception in the presence of background noise was also impaired, with FRDA listeners typically able to access only around 50% of the information available to their normal peers. The use of personal FM-listening devices did however, dramatically improve their ability to hear and communicate in everyday listening situations.

Effects of mild heat shocks at young age on aging and longevity in Drosophila melanogaster.

Young adult flies were submitted to heat shocks (37 degrees C) of various durations (5, 10, 20, 40 or 60 min daily) for 1, 2 or 3 weeks. A slight longevity increase, in both sexes, was only observed with the lowest heat shock. Longer shocks had neutral or negative effects. Flies submitted to the procedure providing a longevity increase did not show a delayed behavioral aging but survived longer at 37 degrees C than control flies. This higher thermotolerance was not associated with an increased hsp70 induction. The results are discussed in connection with hormesis and previous results showing that hypergravity, an other mild stress, increases longevity and delays behavioral aging: different mild stresses may have contrasting effects on aging and longevity.

Oxidative stress, aging and longevity in Drosophila melanogaster.

Free radicals produced during normal metabolism cause damage to macromolecules. The free radical theory of aging proposes that the organism is unable to repair all of them and that, with time, unrepaired damages accumulate and put the organism at risk: in other words, free radicals provoke aging and death. This article reviews both the results of adding antioxidants to food on longevity in Drosophila melanogaster, as well as the studies on antioxidant enzymes (inactivation in vivo, null mutants, overexpression). It is concluded that antioxidant enzymes are probably poorly connected to the normal aging process, but they allow the organism to cope with stressful conditions.

Gerontologists and the media in a time of gerontology expansion.

Gerontology research is now of high concern, particularly to the media, and a risk could exist that gerontologists may give people false hopes or premature conclusions. This article describes two examples: the hypothesis that median longevity will be 150 years in 2100, and the recent results on telomerase. It is concluded that it is prudent for gerontologists to maintain a cautious attitude with the media.

A mild stress due to hypergravity exposure at young age increases longevity in Drosophila melanogaster males.

Drosophila melanogaster flies were exposed to hypergravity starting at two days of age, the range of gravity levels used being 2.58-7.38 g. No longevity change was observed for exposures of less than 14 days. The longevity of males increased if they were submitted to hypergravity for durations ranging from 14 to 24 days. This increase in longevity was never observed in females. The positive effect of exposure to hypergravity has been replicated in two laboratories using two wild-type strains and different rearing conditions. A short hypergravity exposure seems to be a mild stress, yielding positive effects on longevity. This is in accordance with two previous studies showing a slight longevity increase after heat shock in the nematode Caenorhabditis elegans and in Drosophila melanogaster.

Evolutionary theories of aging. 2. The need not to close the debate.

BACKGROUND: Keller and Genoud [Gerontology 1999;45: 336-338] consider that a previous article of Le Bourg [Gerontology 1998;44:345-348] is an inappropriate criticism of evolutionary theories of aging and offer a refutation of this article. OBJECTIVE: We answer that the article was not devoted to the criticism of evolutionary theories of aging but, rather, to the sometimes fast tackling of these theories on what is observed in the wild. Furthermore, we answer to the specific points contained in the Keller and Genoud's article (longevity of ants, reproduction in mammals, and the case of the human species). CONCLUSION: The debate about evolutionary theories of aging is not closed: it would be an error to try to do it before a consensus has been reached.

A review of the effects of microgravity and of hypergravity on aging and longevity.

This article reviews the literature dealing with the effects of acute or chronic exposure to microgravity (spacecrafts) or hypergravity (centrifuge) on longevity and the aging process. Even if space flights are now common, the effects of these two kinds of environment on aging are still poorly documented, particularly in mammals. However, there is a growing interest for the use of the fruit fly Drosophila melanogaster, and this species may be now considered as a model organism in gravitational biology studies dealing with aging.

Resistance to stress as a function of age in Drosophila melanogaster living in hypergravity.

Male and female fruitflies (Drosophila melanogaster) living at different gravity levels [1g: terrestrial gravity; 3 and 5g: hypergravity (HG)] were used to investigate the age-specific (young: 7 days; middle-aged: 28 days; and old: 49 days) resistance to various stresses (starvation, desiccation, and cold). The experiment showed that the resistance of the flies to the studied stresses decreased with age, except in the case of females submitted to starvation which was increased. These variations were explained by the amount of lipid. Variation in desiccation resistance was not explained by the amount of water. As a function of gravity, no or slight differences were observed for the studied stresses. The resistance to heat of young flies increased with the gravity level. This resistance was not explained by a decreased locomotor activity of HG-living flies during heat stress, nor by the water and lipid contents.

HSP70 induction may explain the long-lasting resistance to heat of Drosophila melanogaster having lived in hypergravity.

In this study, we showed that in flies kept for 2 weeks at 1 (terrestrial gravity), 3 or 5 x g (hypergravity, HG) before transfer to 1 x g, resistance to heat remained higher in HG flies for several weeks after the transfer. The measurement of heat shock protein 70 (hsp70) indicated no induction of the protein in HG, but the study revealed that flies living in HG expressed more hsp70 only after being submitted to severe stress. The higher induction of hsp70 may explain the higher thermotolerance of these HG-treated young flies. Finally, an unknown protein was observed only in females. This protein may belong to a class of higher molecular weight hsp (hsp110), which have not previously been observed in Drosophila.

A mild stress, hypergravity exposure, postpones behavioral aging in Drosophila melanogaster.

Flies were submitted to two weeks of hypergravity in a centrifuge (3 or 5 g), starting at the second day of imaginal life, and their behavior (spontaneous locomotor activity, patterns of movement, and climbing activity) was observed from removal of the centrifuge to an older age; the usual effects of age on these behaviors were generally observed. Hypergravity-kept flies had worse behavioral scores on removal of centrifuge than those always kept at 1 g. When they aged, they got either similar or better scores than 1 g flies, which indicates that their behavioral aging may be slower. These results show that a mild stress such as hypergravity, which has been previously shown to increase the longevity of males and resistance to heat shock in both sexes, is an environmental manipulation postponing aging in flies.

Evolutionary theories of aging: handle with care.

BACKGROUND: Evolutionary theories are considered by a growing number of gerontologists as providing a basis to understand why aging occurs. OBJECTIVE: In such conditions, a risk could exist to favor evolutionary explanations rather than nonevolutionary ones, even when both equally fit the data. METHODS: A paper recently published on longevity in ants is analyzed, and a study of fertility and longevity in human beings is done to illustrate this risk. RESULTS: In the two cases, evolutionary and concurrent hypotheses may apply to the same data. CONCLUSIONS: When both kinds of explanations may be applied, the way to solve the problem is not to favor one explanation by relying on a priori preferences, particularly if the favored hypothesis is still controversial.

Hypergravity and aging in Drosophila melanogaster. 9. Conditioned suppression and habituation of the proboscis extension response.

In a first experiment, the conditioned suppression of the proboscis extension response (PER) to sucrose was measured in young, middle-aged and old male Drosophila melanogaster flies living at either 1, 3 or 5 g. Flies were starved and then subjected to a learning task involving a sucrose stimulus, followed by an aversive one applied to their forelegs. In this learning task, flies learn to not extend their proboscis when walking on sucrose. Flies which have lived in hypergravity (HG) had a lower number of PER suppressions than 1 g ones, and this finding was mainly due to young and middle-aged flies. In a second experiment, the habituation of the PER was studied using as stimulation sucrose solutions 2-fold (first experiment), 4-fold (second one) or 8-fold (third one) higher than the individual sucrose threshold. Middle-aged and old flies habituated more slowly than young flies in the second and third experiments. In the third experiment, a decreasing speed of habituation was observed when gravity increased; this result was mainly due to young flies, and no gravity effect was observed in the other two age groups. This whole set of results suggests that HG-kept flies do not age faster than 1 g ones, as far as these learning and habituation tasks are concerned. It seems possible that HG acts like a mild stress to which flies adapt; if applied for a long time, HG could induce a premature aging, as observed in the previous papers of this series.

Increased longevity and resistance to heat shock in Drosophila melanogaster flies exposed to hypergravity.

In recent years, attempts have been made to increase longevity in animal models (caloric restriction in rodents or overexpression of catalase and superoxide dismutase in transgenic flies, for instance). We report here that flies submitted to hypergravity (3 or 5 g), for 1 or 4 weeks starting from the second day of imaginal life and transferred after that time to 1 g, have a higher resistance to heat shock than flies living continuously at 1 g. Furthermore, male flies that had lived for 2 weeks from the second day of life at 3 or 5 g, lived longer than those living all the time at 1 g; no longevity increase was observed in females. As far as we know, this is the first example in flies showing that a mild stress at a young age not only increases resistance to an acute stress but also increases longevity. A hypothesis to explain these results could be that heat-shock proteins, which are induced by various stress factors, are synthesized in conditions of hypergravity.

Correlational analysis in comparative gerontology: an examination of some problems.

Correlation coefficients are widely used in comparative gerontology. However, due to many pitfalls, only a poor knowledge can be gained from these studies in many cases. For instance, a few variables gathered from few species may be used, with no attention to possible confounding variables giving spurious correlations. This article describes some of these problems and proposes to use more thoroughly multivariate analysis in comparative gerontology.

Failure to confirm increased longevity in Drosophila melanogaster submitted to a food restriction procedure.

Several studies have shown that, contrary to what occurs in rodents and in some invertebrate species, food restriction has no positive effect on longevity in Drosophila melanogaster. However, Chippindale et al. (1993) reported that flies subjected to food restriction, by modulating the yeast level, could live longer. In the present study we used the same yeast levels as Chippindale et al. in an attempt to confirm these results. No positive effect of food restriction on longevity could be observed in either sex in mated and virgin flies.

Hypergravity and aging in Drosophila melanogaster. 8. Proboscis-extension-response threshold to sucrose.

The proboscis extension response threshold to sucrose has been measured in young, middle-aged and old male Drosophila melanogaster flies living at a gravity level of 1, 3.02 or 5.02 g until the experiment. The threshold increased with age and no effect of gravity level was observed at any age. These data are at variance with those of previously studied behavioral traits which showed that flies living in hypergravity seemed to age faster than 1-g ones.