Fluorescent pigment and pentane production by lipid peroxidation in honey bees, Apis mellifera

Diversity and function of fluorescent molecules in marine animals

Fluorescence in marine animals has mainly been studied in Cnidaria but is found in many different phyla such as Annelida, Crustacea, Mollusca, and Chordata. While many fluorescent proteins and molecules have been identified, very little information is available about the biological functions of fluorescence. In this review, we focus on describing the occurrence of fluorescence in marine animals and the behavioural and physiological functions of fluorescent molecules based on experimental approaches. These biological functions of fluorescence range from prey and symbiont attraction, photoprotection, photoenhancement, stress mitigation, mimicry, and aposematism to inter- and intraspecific communication. We provide a comprehensive list of marine taxa that utilise fluorescence, including demonstrated effects on behavioural or physiological responses. We describe the numerous known functions of fluorescence in anthozoans and their underlying molecular mechanisms. We also highlight that other marine taxa should be studied regarding the functions of fluorescence. We suggest that an increase in research effort in this field could contribute to understanding the capacity of marine animals to respond to negative effects of climate change, such as rising sea temperatures and increasing intensities of solar irradiation.

Autofluorescent Biomolecules in Diptera: From Structure to Metabolism and Behavior

Light-based phenomena in insects have long attracted researchers’ attention. Surface color distribution patterns are commonly used for taxonomical purposes, while optically-active structures from Coleoptera cuticle or Lepidoptera wings have inspired technological applications, such as biosensors and energy accumulation devices. In Diptera, besides optically-based phenomena, biomolecules able to fluoresce can act as markers of bio-metabolic, structural and behavioral features. Resilin or chitinous compounds, with their respective blue or green-to-red autofluorescence (AF), are commonly related to biomechanical and structural properties, helpful to clarify the mechanisms underlying substrate adhesion of ectoparasites’ leg appendages, or the antennal abilities in tuning sound detection. Metarhodopsin, a red fluorescing photoproduct of rhodopsin, allows to investigate visual mechanisms, whereas NAD(P)H and flavins, commonly relatable to energy metabolism, favor the investigation of sperm vitality. Lipofuscins are AF biomarkers of aging, as well as pteridines, which, similarly to kynurenines, are also exploited in metabolic investigations. Beside the knowledge available in Drosophila melanogaster, a widely used model to study also human disorder and disease mechanisms, here we review optically-based studies in other dipteran species, including mosquitoes and fruit flies, discussing future perspectives for targeted studies with various practical applications, including pest and vector control.

The adult lifespan of the female honey bee (Apis mellifera): Metabolic rate, AGE pigment and the effect of dietary fatty acids

Female honey bees can be queens or workers and although genetically identical, workers have an adult lifespan of weeks while queens can live for years. The mechanisms underlying this extraordinary difference remain unknown. This study examines three potential explanations of the queen-worker lifespan difference. Metabolic rates were similar in age-matched queens and workers and thus are not an explanation. The accumulation of fluorescent AGE pigment has been successfully used as a good measure of cellular senescence in many species. Unlike other animals, AGE pigment level reduced during adult life of queens and workers. This unusual finding suggests female honey bees can either modify, or remove from their body, AGE pigment. Another queen-worker difference is that, as adults, workers eat pollen but queens do not. Pollen is a source of polyunsaturated fatty acids. Its consumption explains the queen-worker difference in membrane fat composition of female adult honey bees which has previously been suggested as a cause of the lifespan difference. We were able to produce "queen-worker" membrane differences in workers by manipulation of diet that did not change worker lifespan and we can, thus, also rule out pollen consumption by workers as an explanation of the dramatic queen-worker lifespan difference.

Reviewing the relevance of fluorescence in biological systems

Fluorescence is emitted by diverse living organisms. The analysis and interpretation of these signals may give information about their physiological state, ways of communication among species and the presence of specific chemicals. In this manuscript we review the state of the art in the research on the fluorescence emitted by plant leaves, fruits, flowers, avians, butterflies, beetles, dragonflies, millipedes, cockroaches, bees, spiders, scorpions and sea organisms and discuss its relevance in nature.

Flight restriction prevents associative learning deficits but not changes in brain protein-adduct formation during honeybee ageing

Honeybees (Apis mellifera) senesce within 2 weeks after they discontinue nest tasks in favour of foraging. Foraging involves metabolically demanding flight, which in houseflies (Musca domestica) and fruit flies (Drosophila melanogaster) is associated with markers of ageing such as increased mortality and accumulation of oxidative damage. The role of flight in honeybee ageing is incompletely understood. We assessed relationships between honeybee flight activity and ageing by simulating rain that confined foragers to their colonies most of the day. After 15 days on average, flight-restricted foragers were compared with bees with normal (free) flight: one group that foraged for ∼15 days and two additional control groups, for flight duration and chronological age, that foraged for ∼5 days. Free flight over 15 days on average resulted in impaired associative learning ability. In contrast, flight-restricted foragers did as well in learning as bees that foraged for 5 days on average. This negative effect of flight activity was not influenced by chronological age or gustatory responsiveness, a measure of the bees' motivation to learn. Contrasting their intact learning ability, flight-restricted bees accrued the most oxidative brain damage as indicated by malondialdehyde protein adduct levels in crude cytosolic fractions. Concentrations of mono- and poly-ubiquitinated brain proteins were equal between the groups, whereas differences in total protein amounts suggested changes in brain protein metabolism connected to forager age, but not flight. We propose that intense flight is causal to brain deficits in aged bees, and that oxidative protein damage is unlikely to be the underlying mechanism.

Extended longevity of queen honey bees compared to workers is associated with peroxidation-resistant membranes

In the honey bee (Apis mellifera), depending on what they are fed, female eggs become either workers or queens. Although queens and workers share a common genome, the maximum lifespan of queens is an order-of-magnitude longer than workers. The mechanistic basis of this longevity difference is unknown. In order to test if differences in membrane composition could be involved we have compared the fatty acid composition of phospholipids of queen and worker honey bees. The cell membranes of both young and old honey bee queens are highly monounsaturated with very low content of polyunsaturates. Newly emerged workers have a similar membrane fatty acid composition to queens but within the first week of hive life, they increase the polyunsaturate content and decrease the monounsaturate content of their membranes, probably as a result of pollen consumption. This means their membranes likely become more susceptible to lipid peroxidation in this first week of hive life. The results support the suggestion that membrane composition might be an important factor in the determination of maximum lifespan. Assuming the same slope of the relationship between membrane peroxidation index and maximum lifespan as previously observed for mammal and bird species, we propose that the 3-fold difference in peroxidation index of phospholipids of queens and workers is large enough to account for the order-of-magnitude difference in their longevity.

The potential of the hydrocarbon breath test as a measure of lipid peroxidation

The straight chain aliphatic hydrocarbons ethane and pentane have been advocated as noninvasive markers of free-radical induced lipid peroxidation in humans. In in vitro studies, the evolution of ethane and pentane as end products of n-3 and n-6 polyunsaturated fatty acids, respectively, correlates very well with other markers of lipid peroxidation and even seems to be the most sensitive test available. In laboratory animals the use of both hydrocarbons as in vivo markers of lipid peroxidation has been validated extensively. Although there are other possible sources of hydrocarbons in the body, such as protein oxidation and colonic bacterial metabolism, these apparently are of limited importance and do not interfere with the interpretation of the hydrocarbon breath test. The production of hydrocarbons relative to that of other end products of lipid peroxidation depends on variables that are difficult to control, such as the local availability of iron(II) ions and dioxygen. In addition, hydrocarbons are metabolized in the body, which especially influences the excretion of pentane. Because of the extremely low concentrations of ethane and pentane in human breath, which often are not significantly higher than those in ambient air, the hydrocarbon breath test requires a flawless technique regarding such factors as: (1) the preparation of the subject with hydrocarbon-free air to wash out ambient air hydrocarbons from the lungs, (2) the avoidance of ambient air contamination of the breath sample by using appropriate materials for sampling and storing, and (3) the procedures used to concentrate and filter the samples prior to gas chromatographic determination. For the gas chromatographic separation of hydrocarbons, open tubular capillary columns are preferred because of their high resolution capacity. Only in those settings where expired hydrocarbon levels are substantially higher than ambient air levels might washout prove to be unnecessary, at least in adults. Although many investigators have concentrated on one marker, it seems preferable to measure both ethane and pentane concurrently. The results of the hydrocarbon breath test are not influenced by prior food consumption, but both vitamin E and beta-carotene supplementation decrease hydrocarbon excretion. Nevertheless, the long-term use of a diet high in polyunsaturated fatty acids, such as in parenteral nutrition regimens, may result in increased hydrocarbon exhalation. Hydrocarbon excretion slightly increases with increasing age. Short-term increases follow physical and intellectual stress and exposure to hyperbaric dioxygen.(ABSTRACT TRUNCATED AT 400 WORDS)

An alternative explanation for anomalies in "soluble lipofuscin" fluorescence data from insects, crustaceans, and other aquatic species

Published attempts to extract lipofuscin from crustaceans and fish to assess age for fisheries research purposes have used essentially the same extraction methodology applied to insects, but have neither shown a conclusive age-dependence of spectrally similar fluorescence nor proved its association with lipofuscin. The reported lipofuscin solvent extraction method for fleshflies, Sarcophaga bullata, was manipulated by varying wash volume. This revealed that almost all age-dependent blue fluorescent material persisting in lipid fractions was actually pteridine-like. This finding was consistent with some previous independent results for Musca domestica. Examination of reported lipofuscin extraction protocols for other insects suggested that this problem was probably widespread. The pteridines are known to occur in unusually high amounts in insects, accumulating with age specifically in some members of this group by storage excretion, probably as a terrestrial water conservation strategy. In addition, there is growing evidence in the gerontological literature for other groups that solvent extracted blue fluorescence is not a true measure of lipofuscin content in tissues. These findings provide considerable insight into anomalies in putative lipofuscin fluorescence data between the insects and various aquatic species and suggest that there may be little basis for expectations of age-dependent fluorescence from aquatic species when the same gross extraction and crude purification methods are used.

In vivo lipid peroxidation in man as measured by the respiratory excretion of ethane, pentane, and other low-molecular-weight hydrocarbons

A method for the collection and measurement of low-molecular-weight volatile hydrocarbons exhaled in human breath as a result of lipid peroxidation in vivo is described. Subjects breathed in a closed-circuit rebreathe system and samples were taken over a 2-h period, extracted, and analyzed by gas-liquid chromatography isothermally on a 3-m column of n-octane/Porasil-C. Immediately, prior to rebreathing subjects were equilibrated with scrubbed air containing very low ambient levels of hydrocarbons to eliminate the effects of previous exposure to hydrocarbon-contaminated environments. Only under these conditions could hydrocarbon exhalation be measured. In the rebreathe system C3-C5 hydrocarbon concentrations increased linearly initially but reached a steady state after 1.5 h while ethane did not approach equilibrium even after 2 h. The steady-state equilibrium was demonstrated to be due to tissue uptake and metabolism of the hydrocarbon gases. Ethane metabolism was slow, allowing calculation of the endogenous production from the initial rate of change in concentration and an experimentally determined total body solubility coefficient. Similar calculations for pentane were not valid as metabolism was rapid; therefore production was estimated from the equilibrium value reached after 2 h. Ethane production in six healthy subjects was calculated to be 95.1 +/- 19.0 pmol/kg/h while equilibrium values for pentane were 120 +/- 50 pmol/liter. This method now allows the quantitation in man of lipid peroxidation in vivo.

Effect of age and ambient temperature on n-pentane production in adult housefly, Musca domestica

The objective of this study was to examine the relationship between lipid peroxidation and aging in the male housefly. Metabolic rate of flies is known to be higher and life span shorter at elevated ambient temperature. Evolution of n-pentane and level of thiobarbituric acid (TBA) reactive material were used as indicators of lipid peroxidation. n-Pentane accumulated by houseflies in vivo and by whole body homogenates of houseflies, in response to tert-butyl hydroperoxide (1 mM), increased with age. n-Pentane accumulation in vivo was markedly higher at higher ambient temperature. Furthermore, n-pentane generated by flies in vivo and by fly homogenates in vitro tended to be lower in flies raised at a lower ambient temperature. TBA-reactive material, elicited by tert-butyl hydroperoxide, was augmented in older flies, but no significant difference was found between flies aged at different ambient temperatures. Analysis of fatty acids in housefly homogenates indicated an age-associated increase in the ratio of polyunsaturated to saturated fatty acids.

Age and oxygen toxicity related fluorescence in the honey bee thorax

The blue fluorescent material in thoraxes of honey bees of known adult age from eclosion to 28 days was measured. The amount was greater in older insects and exposure to ozone (ppm) augmented the rate of accumulation. The nearly constant daylight flying by the bees and the ozone effect suggest radical peroxidative origin of the fluorescence. The material was partially purified by chromatography. It is a relatively non-polar lipid.

Effect of vitamin E on pentane exhaled by rats treated with methyl ethyl ketone peroxide

One useful method to monitor in vivo lipid peroxidation is the measurement of volatile hydrocarbons, mainly pentane and ethane, that derive from unsaturated fatty acid hydroperoxides. Vitamin E, the biological antioxidant, inhibits lipid peroxidation and the production of pentane and ethane. The rates of pentane production by male Sprague-Dawley rats fed a diet that contained 10% vitamin E-stripped corn oil and 0, 1, 3, 5 or 10 IU dl-alpha-tocopherol acetate/kg were monitored over a 12-wk period. During the eleventh and twelfth weeks, the rats were injected intraperitoneally with 3.3 and 13 mg of methyl ethyl ketone peroxide (MEKP)/kg body wt, respectively. Pentane production was then measured at intervals over a 50-min period, and the total amount of pentane produced over this time interval was estimated. An asymptotic function was found to describe the relationship between exhaled pentane and the low levels of dietary vitamin E that were fed to the rats. As measured by pentane production, rats had a higher minimal vitamin E requirement after they were treated with the potent peroxidation initiator MEKP than they did prior to treatment. The level of pentane exhaled by rats injected with 13 mg MEKP/kg body wt was significantly correlated with kidney and spleen tocopherol levels.

Fluorescent age pigment in insect lysosomes

Fluorescent pigment accumulates in the lysosomal fraction of spodoptera sixth instars. It was purified by silicic acid chromatography. The fluorescent fraction was characterized by conjugated unsaturation, reactivity with thiobarbituric acid, and lability in alkali; all reminiscent of age pigment. The phosphorus content of the purified fraction was negligible and nitrogen was not detected. It is suggested that the material is degraded, perhaps polymerized lipid fragments.

The composition of alkanes in exhaled air of rats as a result of lipid peroxidation in vivo. Effects of dietary fatty acids, vitamin E and selenium

Alkane production in exhaled air of rats has been studied as an index of lipid peroxidation in vivo in these animals. The effect of feeding essential fatty acid-deficient rats varying levels of n-4, n-6 and n-7 polyunsaturated fatty acids for various periods of time has been studied with regard to the composition of the alkanes produced as well as the fatty acid composition of liver phospholipids and liver and adipose tissue triacylglycerols. It was found that the fatty acid composition of liver lipids depended markedly on the nature and the quantity of polyunsaturated fatty acid in the diet. The composition of the alkanes produced on stimulation of lipid peroxidation in vivo by inhalation of small, non-lethal doses of carbon tetrachloride corresponded closely to the fatty acid composition of the liver phospholipids. The results strongly suggest that the alkanes produced as a result of lipid peroxidation in vivo originate from the methyl end of the fatty acid administered. So ethane is produced from n-3 acid, propane from n-4 acid, pentane from n-6 acid and hexane from n-7 acid. The amounts of a specific alkane produced increase as its corresponding fatty acid, as present in the liver phospholipids, increases. There are indications that relatively more ethane than pentane is produced on stimulation of the in vivo lipid peroxidation although there are considerably more n-6 fatty acids than n-3 fatty acids present in the liver phospholipids.