Balance between macronutrients affects life span and functional senescence in fruit fly Drosophila melanogaster

It has recently been demonstrated that as the ratio of protein to carbohydrate (P:C) in the diet declines, life span increases in Drosophila. Here we explored how extremely low dietary ratios of protein to carbohydrate affected longevity and a selection of variables associated with functional senescence. An increase in P:C ratio from 1:57 to 1:20 shortened life span by increasing age-dependent mortality; whereas a further decline in P:C from 1:57 to 1:95 caused a modest decrease in life span. Female flies consuming the 1:20 and 1:38 diets laid more eggs than those consuming the lower P:C diets. Flies fed diets with higher ratios were more resistant to heat stress. Flies consuming the diets with lowest P:C ratios needed more time to restore activity after paralysis. Our study has therefore extended to very low P:C ratios available data demonstrating that dietary P:C ratio affects life span, fecundity and heat stress resistance, with fecundity and heat stress responses showing the opposite trend to life span.     

Aloe vera or resveratrol supplementation in larval diet delays adult aging in the fruit fly, Drosophila melanogaster

Longevity extension in Drosophila melanogaster by feeding diet supplemented with chemicals throughout adulthood can cause harmful side effects. We tested the effect of larval diet supplementation with five different concentrations of resveratrol and one concentration of Aloe vera extract on the adult longevity of short-lived D melanogaster populations. Resveratrol and A vera extract supplementation of larval diet extended adult longevity in both the male and female flies without reducing fecundity but by efficient reactive oxygen species scavenging through increased antioxidant enzymes activity and better neuroprotection as indicated by increased locomotor activity in adult males.     

Conditioned Behavior in Drosophila melanogaster

Populations of Drosophila were trained by alternately exposing them to two odorants, one coupled with electric shock. On testing, the flies avoided the shock-associated odor. Pseudoconditioning, excitatory states, odor preference, sensitization, habituation, and subjective bias have been eliminated as explanations. The selective avoidance can be extinguished by retraining. All flies in the population have equal probability of expressing this behavior. Memory persists for 24 hr. Another paradigm has been developed in which flies learn to discriminate between light sources of different color.     

Drosophila melanogaster antimicrobial defense

The Drosophila melanogaster host defense is complex but remarkably efficient. It is a multifaceted response to a variety of fungal, bacterial, and parasitic invaders. Current knowledge is discussed on recognition of infectious microorganisms and on the activation of intracellular signaling cascades that concur with the expression of numerous immune-responsive genes, among which, to date, the most prominent appear to encode potent antimicrobial peptides.     

Transplantation of Nuclei in Drosophila melanogaster

Nuclei surrounded by ooplasm of the syncytial stage of developing eggs of wild-type Drosophila melanogaster were implanted into freshly laid fertilized eggs of females of a y w stock. More than half of the recipient eggs produced larvae, but few of the larvae hatched or developed further. The best sets of experiments gave about twelve percent of imagos, mostly y w in appearance. Several larvae were mosaics with yellow Malpighian tubes, and two flies had part of the abdominal segments of the wild type. Half of the flies were fertile, but they produced only y w offspring, except for two males that had y w appearance, but wild-type gonads. When crossed with y w females, they gave wild-type females and y w males.     

Age-associated cardiac dysfunction in Drosophila melanogaster

The fruit fly, Drosophila melanogaster, has served as a valuable model/organism for the study of aging and was the first organism possessing a circulatory system to have its genome completely sequenced. However, little is known about the function of the heartlike organ of flies during the aging process. We have developed methods for studying cardiac function in vivo in adult flies. Using 2 different cardiovascular stress methods (elevated ambient temperature and external electrical pacing), we found that maximal heart rate is significantly and reproducibly reduced with aging in Drosophila, analogous to observations in elderly humans. We also describe for the first time several other aspects of the cardiac physiology of young adult and aging Drosophila, including an age-associated increase in rhythm disturbances. These observations suggest that the study of declining cardiac function in aging flies may serve as a genetically tractable model for genome-wide mutational screening for genes that participate in or protect against cardiac aging and disease.     

Spontaneous Recombination in Drosophila melanogaster Males

A second chromosome of Drosophila melanogaster (symbol T-007) isolated from a natural population in Harlingen, Texas, was found to undergo recombination in heterozygous males. Heterozygous males transmit this chromosome with a frequency, k, of about 0.4, considerably reduced from the expected value of 0.5. The frequency of male recombination and the k value are negatively correlated, indicating that the two phenomena are in some way related. The complementary recombinant products are recovered in equal frequency and the recombination is not restricted to the heterochromatic regions. The time of recombination is not certain, but the distribution of recombinants is more suggestive of meiotic than of premeiotic occurrence. In the natural population of these flies, the frequency of chromosomes with male recombination is 20% or more.     

Low oxygen delays fibroblast senescence despite shorter telomeres

It has been widely accepted that telomere shortening acts as a cell division counting mechanism that beyond a set critical length signals cells to enter replicative senescence. In this study, we demonstrate that by simply lowering the oxygen content of the cell culture environment 10-fold (20–2%) extends the replicative lifespan of fetal bovine fibroblasts at least five-times (30–150 days). Although, low oxygen fibroblasts display a slightly slower rate (P > 0.05) of telomere attrition than their high oxygen counterparts (171 bp versus 182 bp/PD), late passage fibroblasts (>50 PD) that have extended their replicative capacity under low oxygen conditions exhibited significantly (P < 0.05) shorter telomere lengths (11,135 ± 467 bp) compared to senescent cells (25–34 PD) cultured under high oxygen conditions (14,827 ± 1173 bp). There was a significant increase (P < 0.05) in chromosomal abnormalities with continual cell division under both high and low oxygen environments, however, fibroblasts displayed a significant reduction (P < 0.001) in chromosomal abnormalities at low oxygen tensions compared to those under 20% oxygen. These apparent protective effects on telomere shortening, delayed senescence and reduced chromosomal aberrations may be attributed to the up-regulation of telomerase activity observed for fibroblasts cultured under low oxygen. These results are consistent with the idea that a critically short telomere length may not be the sole trigger of replicative senescence, but may be regulated by the integrity of telomere structure itself and/or the amount of oxidative DNA damage in the cell.     

Clock Mutants of Drosophila melanogaster

Three mutants have been isolated in which the normal 24-hour rhythm is drastically changed. One mutant is arrhythmic; another has a period of 19 hr; a third has a period of 28 hr. Both the eclosion rhythm of a population and the locomotor activity of individual flies are affected. All these mutations appear to involve the same functional gene on the X chromosome.     

Gut-associated microbes of Drosophila melanogaster

There is growing interest in using Drosophila melanogaster to elucidate mechanisms that underlie the complex relationships between a host and its microbiota. In addition to the many genetic resources and tools Drosophila provides, its associated microbiota is relatively simple (1–30 taxa), in contrast to the complex diversity associated with vertebrates (> 500 taxa). These attributes highlight the potential of this system to dissect the complex cellular and molecular interactions that occur between a host and its microbiota. In this review, we summarize what is known regarding the composition of gut-associated microbes of Drosophila and their impact on host physiology. We also discuss these interactions in the context of their natural history and ecology and describe some recent insights into mechanisms by which Drosophila and its gut microbiota interact.

“Workers with Drosophila have been considered fortunate in that they deal with the first multicellular invertebrate to be cultured monoxenically (Delcourt and Guyenot, 1910); the first to be handled axenically on a semisynthetic diet (Guyenot, 1917); and the first to be grown on a defined diet (Schultz et al., 1946). This list of advantages is somewhat embarrassing, since it implies an interest in nutrition that, in reality, was only secondary. The very first studies were concerned with the reduction of variability in genetic experiments (Delcourt and Guyenot, 1910) and standardization of the nutritional environment.”

-James Sang, 1959 Ann NY Acad ¹     

Gut-associated microbes of Drosophila melanogaster

There is growing interest in using Drosophila melanogaster to elucidate mechanisms that underlie the complex relationships between a host and its microbiota. In addition to the many genetic resources and tools Drosophila provides, its associated microbiota is relatively simple (1-30 taxa), in contrast to the complex diversity associated with vertebrates (> 500 taxa). These attributes highlight the potential of this system to dissect the complex cellular and molecular interactions that occur between a host and its microbiota. In this review, we summarize what is known regarding the composition of gut-associated microbes of Drosophila and their impact on host physiology. We also discuss these interactions in the context of their natural history and ecology and describe some recent insights into mechanisms by which Drosophila and its gut microbiota interact. "Workers with Drosophila have been considered fortunate in that they deal with the first multicellular invertebrate to be cultured monoxenically (Delcourt and Guyenot, 1910); the first to be handled axenically on a semisynthetic diet (Guyenot, 1917); and the first to be grown on a defined diet (Schultz et al., 1946). This list of advantages is somewhat embarrassing, since it implies an interest in nutrition that, in reality, was only secondary. The very first studies were concerned with the reduction of variability in genetic experiments (Delcourt and Guyenot, 1910) and standardization of the nutritional environment." -James Sang, 1959 Ann NY Acad ( 1).     

Reproductive fitness and longevity in Drosophila melanogaster

It has been suggested that senescence could have evolved by selection of genes with beneficial effects early in life and detrimental ones later in life (pleiotropy theory of the evolution of senescence). To test that theory, the egg production of 322 females of the Oregon strain of Drosophila melanogaster was recorded daily throughout their life. At the individual level, no relation could be detected between early components of fitness and longevity. For the time being it appears that there are no unequivocal reasons to accept the pleiotropy theory of the evolution of senescence.     

The circadian clock in old Drosophila melanogaster

A growing body of evidence indicates that one of theage-associated changes in the central nervous systemthat affect most old people is the loss of functionof the circadian clock system. This loss results inimpaired timing and quality of sleep, with consequentcognitive and other behavior problems. Failure of theclock contributes to the difficulties encountered withAlzheimer's disease. It also results in adversechanges in the hormonal regulation of intermediarymetabolism, stress resistance and sexual function.Drosophila melanogaster is proposed as a modelorganism where this age-related change may be studiedmore readily. Circadian patterns are disrupted inDrosophila, with considerable differences betweenstrains. In addition a fusion gene product of a keygene involved in the clock (per), and GreenFluorescent Protein, shows a 50% fall with age.     

Molecular vibration-sensing component in Drosophila melanogaster olfaction

A common explanation of molecular recognition by the olfactory system posits that receptors recognize the structure or shape of the odorant molecule. We performed a rigorous test of shape recognition by replacing hydrogen with deuterium in odorants and asking whether Drosophila melanogaster can distinguish these identically shaped isotopes. We report that flies not only differentiate between isotopic odorants, but can be conditioned to selectively avoid the common or the deuterated isotope. Furthermore, flies trained to discriminate against the normal or deuterated isotopes of a compound, selectively avoid the corresponding isotope of a different odorant. Finally, flies trained to avoid a deuterated compound exhibit selective aversion to an unrelated molecule with a vibrational mode in the energy range of the carbon-deuterium stretch. These findings are inconsistent with a shape-only model for smell, and instead support the existence of a molecular vibration-sensing component to olfactory reception.     

Ecdysteroid receptors in Drosophila melanogaster adult females

Ecdysteroid receptors were identified and partially characterized from total cell extracts of whole animals and dissected tissues from Drosophila melanogaster adult females. Binding studies indicated the presence of two ecdysteroid binding components having high affinity and specificity consistent with receptors previously identified in embryos and larvae. The highest affinity binding component in 3- to 4-day females had a dissociation constant of 9.2 x 10(-10) M and a maximal binding concentration of approximately 90 pmol/g protein, with a lower affinity component having a dissociation constant of 2.94 X 10(-9) M. Receptors at similar concentrations were also observed in abdominal walls containing adult fat body, with relatively lower receptor levels observed in ovaries. These results indicate that the observed ecdysteroid hormone concentrations in adult females can account for a physiological stimulatory effect on yolk protein synthesis in adult fat body.     

Age-related RNA decline in adult Drosophila melanogaster

We investigated the correlation between age and total RNA levels in long-lived and control lines of Drosophila melanogaster. Total RNA was extracted at 10 ages from 1-63 days posteclosion from 3 inbred lines, with replication. Three different methods of RNA quantitation gave highly correlated estimates. Total RNA declined substantially with age, exhibiting a dramatic drop in the first few days of adult life. We find no evidence for a causal relationship between adult longevity and total RNA levels, since long-lived and control lines exhibited similar patterns of age-related RNA decline. These observations suggest that the dramatic decline in total RNA that occurs early in adult life does not explain the twofold differences in life span between lines. The pattern of age-specific decline coincides with published observations on age-specific metabolic rates, and suggests that 14-day-old flies are functionally senescent.     

Determination of Blastoderm Cells in Drosophila melanogaster

A method for culturing blastoderm cells of Drosophila in vivo has been developed that allows these cells to differentiate into larval or adult structures. By intermixture of genetically marked cells from bisected and whole embryos, it was shown that blastoderm cells are restricted in their potential for forming adult epidermal structures. Cells isolated from anterior-half embryos are determined for forming head and thoracic structures, whereas cells from posterior-half embryos are determined for forming thoracic and abdominal structures. The specificity of determination and the localization of determinative factors is discussed.