t-[35S]butylbicyclophosphorothionate binding sites in invertebrate tissues

Specific high affinity binding of the cage convulsant t-[35S]butylbicyclophosphorothionate (TBPS) was observed in membrane homogenates of housefly heads and crayfish abdominal muscles. [35S]TBPS binding in these two invertebrate tissues was inhibited by biologically active cage convulsants, picrotoxin analogs, and barbiturates. The housefly binding sites were inhibited most potently by several insecticides. Approximately 50% of total binding was displaceable by excess (0.1 mM) nonradioactive TBPS, picrotoxinin, ethyl bicyclophosphate, or dieldrin. Optimal binding assay conditions for housefly homogenates included pH 7.5, 22 degrees C temperature, 0.3 M chloride concentration, and incubation for 60 min; for crayfish homogenates, 4 degrees C temperature and 150-min incubations were optimal. Scatchard plots of equilibrium binding indicated one site in both tissues (KD = 50 nM, Bmax = 250 fmol/mg protein in housefly; KD = 25 nM, Bmax = 100 fmol/mg protein in crayfish). Association kinetics in housefly were consistent with one rate constant (k+1 = 8 X 10(6) M-1 min-1), but dissociation was described better by two rate constants (k-1 = 0.28 min-1 and 0.042 min-1; calculated KD values of 80 nM and 12 nM). Displacement by cage convulsants showed Hill numbers near 0.5, also consistent with two populations of affinity, while displacement by other drugs showed Hill numbers near 1.0. [35S]TBPS binding in insects was most potently inhibited by the insecticides dieldrin (IC50 = 50 nM), aldrin, and lindane (200 nM), in a stereospecific manner, consistent with this binding site being the receptor for biological toxicity. [35S]TBPS binding was also inhibited by relatively high concentrations of some pyrethroid insecticides, such as deltamethrin and cypermethrin (1-2 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and sequence of cDNA encoding a cytochrome P-450 from an insecticide-resistant strain of the house fly, Musca domestica

A cDNA expression library from phenobarbital-treated house fly (Musca domestica) was screened with rabbit antisera directed against partially purified house fly cytochrome P-450. Two overlapping clones with insert lengths of 1.3 and 1.5 kilobases were isolated. The sequence of a 1629-base-pair (bp) cDNA was obtained, with an open reading frame (nucleotides 81-1610) encoding a P-450 protein of 509 residues (Mr = 58,738). The insect P-450 protein contains a hydrophobic NH2 terminus and a 22-residue cysteine-containing fragment near the COOH terminus that is known to bind the heme; both of these features have been found in the more than five dozen vertebrate P-450 proteins of which the sequences are presently known. Interestingly, the termination codon UAA may be contained in a putative polyadenylylation signal (AAUAAA) of the mRNA. This P-450 protein exhibits the most similarity (27% amino acid positional identity) with mammalian proteins of the P450III family but qualifies as a member of another family, which we propose to designate the P450VI gene family. This cDNA and deduced protein sequence should provide important information in the study of evolution of the P-450 gene superfamily, as well as provide an important probe for studying the regulation of insect P-450 and understanding the molecular genetics of insecticide resistance.

Binding of [3H]batrachotoxinin A-20-alpha-benzoate to a high affinity site associated with house fly head membranes

1. [3H]Batrachotoxinin A-20-alpha-benzoate (BTX-B), a radioligand that labels the alkaloid activator recognition site of the voltage-sensitive sodium channel, was bound specifically to high affinity, saturable sites in a subcellular preparation from house fly (Musca domestica L.) heads that was shown previously to contain binding sites for other sodium channel-directed ligands. 2. Specific binding of [3H]BTX-B was observed in the presence of 140 mM sodium or potassium and was inhibited by choline ion. 3. Saturating concentrations of scorpion (Leiurus quinquestriatus) venom stimulated the specific binding of [3H]BTX-B four-fold, increasing the proportion of specific binding of 10 nM [3H]BTX-B from less than 15% to 40%. Equilibrium dissociation studies in the presence of scorpion venom gave an equilibrium dissociation constant (KD) for [3H]BTX-B of 80 nM and a maximal binding capacity (Bmax) of 1.5 pmol/mg protein. 4. Parallel experiments in the absence of venom gave a KD value of 140 nM and a Bmax of 1.3 pmol/mg protein, indicating that scorpion venom stimulated [3H]BTX-B binding by increasing the affinity of this site approximately two-fold. 5. The specific binding of [3H]BTX-B was inhibited by the sodium channel activators aconitine and batrachotoxin and, to a lesser extent, by the anticonvulsant diphenylhydantoin. However, several other sodium channel-directed neurotoxins known to exert allosteric effects on the binding of [3H]BTX-B to mammalian brain preparations did not affect the binding of [3H]BTX-B to house fly head membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between superoxide anion radical generation and aging in the housefly, Musca domestica

The objective of this study was to elucidate the possible cause of increased oxidative stress observed in the adult housefly during aging. The hypothesis that increased production of oxygen radicals may be a cause of the increased oxidative stress was tested by comparison of 8-day and 15-day old flies, which represent the stage of full maturation and the beginning of the dying phase, respectively. Rates of both antimycin A-resistant respiration of isolated mitochondria and O2 generation at ubiquinone-cytochrome b site by submitochondrial particles increased during aging and were associated with life expectancy of flies. Flies destined to die earlier than their cohorts of the same age exhibited a relatively higher rate of O2- production. Age-related increase in O2- generation was not associated with corresponding changes in ubiquinone content of mitochondria.

'Photo-degeneration' of neurones after extracellular dye application

Irradiation in the presence of a dye applied to the extracellular space was found to trigger neuronal degeneration in fly photoreceptor neurones. This phenomenon endowed the selected cells with a dark and fine-grained label such that they could be traced and scrutinized for synaptic specializations. It also initiated their phagocytotic removal from the neural network. Various states of degeneration fitting classical descriptions could be achieved by acting upon the light dose. The phenomenon seems to rely on photosensitization of the cell by the dye. The simplicity and precision with which this phenomenon can be induced makes 'photo-degeneration' an exciting prospective tool for combined anatomical and physiological studies on (natural) neural networks and may provide a new line of medical applications.

Troponin of asynchronous flight muscle

Troponin has been prepared from the asynchronous flight muscle of Lethocerus (water bug) taking special care to prevent proteolysis. The regulatory complex contained tropomyosin and troponin components. The troponin components were Tn-C (18,000 Mr), Tn-T (apparent Mr 53,000) and a heavy component, Tn-H (apparent Mr 80,000). The troponin was tightly bound to tropomyosin and could not be dissociated from it in non-denaturing conditions. A complex of Tn-T, Tn-H and tropomyosin inhibited actomyosin ATPase activity and the inhibition was relieved by Tn-C from vertebrate striated muscle in the presence of Ca2+. However, unlike vertebrate Tn-I, Tn-H by itself was not inhibitory. Monoclonal antibodies were obtained to Tn-T and Tn-H. Antibody to Tn-T was used to screen an expression library of Drosophila cDNA cloned in lambda phage. The sequence of cDNA coding for the protein was determined and hence the amino acid sequence. The Drosophila protein has a sequence similar to that of vertebrate skeletal and cardiac Tn-T. The sequence extends beyond the carboxyl end of the vertebrate sequences, and the last 40 residues are acidic. Part of the sequence of Drosophila Tn-T is homologous to the carboxyl end of the Drosophila myosin light chain MLC-2 and one anti-Tn-T antibody cross-reacted with the light chain. Lethocerus Tn-H is related to the large tropomyosins of Drosophila flight muscle, for which the amino acid sequence is known, since antibodies that recognize this component also recognize the large tropomyosins. Tn-H is easily digested by calpain, suggesting that part of the molecule has an extended configuration. Electron micrographs of negatively stained specimens showed that Lethocerus thin filaments have projections at about 39 nm intervals, which are not seen on thin filaments from vertebrate striated muscle and are probably due to the relatively large troponin complex. Decoration of the thin filaments with myosin subfragment-1 in rigor conditions appeared not to be affected by the troponin. The troponin of asynchronous flight muscle lacks the Tn-I component of vertebrate striated muscle. Tn-H occurs only in the flight muscle and may be involved in the activation of this muscle by stretch.

Quantitative analyses of the uncoupling activity of substituted phenols with mitochondria from flight muscles of house flies

Uncoupling activity with flight-muscle mitochondria from house flies was measured for a series of weakly acidic uncouplers (substituted phenols) and compared with the protonophoric potency across lecithin liposomal membranes. The activity was linearly related to the protonophoric potency when such factors as the stability of anionic species in the membrane phase and the difference in the pH conditions of the extramembranous aqueous phase were taken into account. Relationships of the flight-muscle activity with activities measured previously with rat-liver mitochondria and spinach chloroplasts were linear. Our findings were further evidence for the shuttle-type mechanism of the uncoupling action of weakly acidic uncouplers.

Heterogeneous glycosylation of Musca domestica arylphorin

Two distinct fractions of Musca domestica arylphorin were isolated by affinity chromatography on Concanavalin A-Sepharose column. The results show that in the hexameric arylphorin that do not bind to the lectin there is no Concanavalin A binding subunit and in the majority of the hexamers that bind to the lectin there is only one subunit with Concanavalin A binding site. The results indicate that the carbohydrate moiety of the arylphorin is not involved in its specific uptake by the fat bodies and integument.

Insecticide-insensitive acetylcholinesterase from a laboratory selected and a field strain of housefly (Musca domestica) (L.)

1. Acetylcholinesterase from the heads of a strain of houseflies selected for resistance to the carbamate insecticide methomyl, and from a methomyl-resistant field strain was found to be less sensitive to inhibition by methomyl than that from a susceptible strain. 2. The enzyme from resistant insects was also more tolerant to malaoxon, dichlorvos and bomyl but not to azamethiphos. 3. The decrease in sensitivity to inhibition appeared to be due to an increase in affinity for substrate.

Effect of hydrogen peroxide administration on life span, superoxide dismutase, catalase, and glutathione in the adult housefly, Musca domestica

The general objective of this study was to further elucidate the relationship between oxidative stress and the aging process. H2O2 is known to be a progenator of reactive oxygen species, such as hydroxyl free radical, by various mechanisms involving, among others, a superoxide anion radical-driven Fenton cycle, or splitting of the 0-0 bond by hemoproteins. Effects of H2O2 administration on life span, activities of superoxide dismutase, catalase, concentrations of endogenous H2O2, and glutathione in the housefly are described. Adult male flies were given various concentrations of H2O2, ranging from 0 to 100 mM H2O2, in their drinking water. Life span was shortened by H2O2 intake except in 10 mM H2O2 administrated flies, which exhibited the longest life span. Flies administered 10 mM H2O2 also contained the highest concentration of reduced glutathione (GSH). Superoxide dismutase and catalase activities were not affected by H2O2 intake. Compensatory elevation in GSH may be responsible for the increase in life span observed in 10 mM H2O2 administered flies.

Correlates of longevity in two strains of the housefly, Musca domestica

The general objective of this study was to identify biochemical correlates of longevity in the housefly by comparing two strains of flies that have different longevities. The average and the maximum life spans of the longer-lived "Cambridge" strain flies were 46% and 23%, respectively, greater than the shorter-lived "Thuron" strain flies. The hypothesis that longer-lived organisms have relatively more efficient mechanisms to minimize oxidative stress and maintain a relatively more reduced redox potential was tested. All measurements were made on 8-day-old male flies maintained under identical conditions. Flies of the longer-lived strain had a lower metabolic rate and contained lesser amounts of H2O2 and thiobarbituric acid-reactants than the flies of the shorter-lived strain. Reduced glutathione concentration and activities of catalase, glutathione reductase and thioltransferase were higher in the longer-lived strain indicating that longer-lived flies manifest lower levels of oxidative stress and greater ability to maintain a relatively more reducing environment than the shorter-lived flies. Superoxide dismutase (SOD) activity was similar in the two strains, but the SOD/metabolic rate ratio was higher in the longer-lived strain. Total activity of glutathione S-transferases was comparable in the two strains suggesting that differences in detoxification ability are not correlated with longevity. Only S-glutamylcysteine synthetase activity was greater in the shorter-lived strain suggesting that variation in longevity is not due to reduction in the ability to synthesize GSH. Overall, the results support the view that parameters associated with oxidative stress play a role in the aging process of the houseflies.

Oxidative metabolism of the GABAA receptor antagonist t-butylbicycloortho[3H]benzoate

1. The trioxabicyclooctane ring of t-butylbicycloortho[3H]benzoate (TBOB), (CH3)3CC(CH2O)3CC6H5, is cleaved to yield the 3-oxo-benzoate, (CH3)3CC(CHO)(CH2OH)CH2OC(O)C6H5, on O-methylene hydroxylation by microsomes from mouse liver or houseflies in the presence of NADPH. 2. The methyl and phenyl substituents are tentatively identified as additional sites of oxidative metabolism. 3. The 3-oxo-benzoate from oxidative cage opening and the bis-(hydroxymethyl)-benzoate, (CH3)3CC(CH2OH)2CH2OC(O)C6H5, from enzymic reduction of the 3-oxo-benzoate undergo esteratic hydrolysis to benzoic acid. 4. Metabolites of TBOB excreted by rats and houseflies include the bis-(hydroxymethyl)-benzoate and benzoic and hippuric acids. 5. Metabolic hydroxylation of TBOB at O-methylene, alkyl and aryl substituents may serve as a model for detoxication reactions of related potent GABAA receptor antagonists and insecticides.

Age-related changes in the redox status of the housefly, Musca domestica

The objective of this study was to further test the hypothesis that aging in the housefly is associated with increased oxidative stress. Age-related changes in the concentration of glutathione, NAD and NADP, which undergo oxidation-reduction reactions, and of H2O2, a potent cellular oxidant, were examined in the homogenates of adult male houseflies at 4, 8, 12 and 16 days of age. Sixteen days of age represents the beginning of the dying phase of the population when about 20% mortality usually occurs. Results indicate that the ratios of reduced/oxidized forms decline with age; H2O2 concentration steadily increases with age. Results suggest that the intracellular redox potential of the housefly becomes progressively more pro-oxidizing or less reducing during the aging process.

Difference in calcium sensitivities of the sodium transporting systems in the nervous system of susceptible and kdr-resistant houseflies, Musca domestica L

1. The synaptosomal preparations from the kdr-resistant strains have lower responsiveness to externally applied Ca2+ than the susceptible counterparts with respect to their Na+/Ca2+ exchange, Na+ uptake, Na+-Ca2+ protein kinase-phosphatase and its phosphorylation activities. 2. In vivo toxicity tests support the above in vitro observation in that the kdr-resistant strain shows a significant cross-resistance to agents known to affect the Na+ channel operations, those which increase intracellular Ca2+ or act as effective Ca2+ substitutes. 3. Such evidence indicates a possibility of a causal relationship between kdr resistance and the reduction of Ca2+ sensitivity by these ATP-utilizing systems including the Na+ transporting systems in the resistant insects.

Pharmacology of putative glutamate receptors from insect skeletal muscles, insect central nervous system and rat brain

Binding of [3H]glutamate to housefly brain and honeybee brain and thoracic muscle membranes as well as to the American cockroach nerve cord was measured in Na+-free Tris-citrate buffer, 2.5 mM CaCl2, pH 7.4. The dissociation constants (KDS) ranged from 0.16 to 1.36 microM, and thoracic muscles had 2-4-fold higher density of receptors than brain tissue. The potent inhibitors of housefly brain binding were in decreasing order of effectiveness: L-glutamate greater than L-aspartate = L-cysteate = ibotenate greater than quisqualate greater than L-homocysteate greater than L-APB greater than L-APV greater than NMDA greater than D-APB greater than D-glutamate, with no inhibition by 100 microM of GDEE, dihydrokainate, D-APV, D-homocysteate or D-aspartate. The drug specificity of [3H]glutamate binding sites in housefly brain was generally similar to that of binding sites in housefly muscle, except that the former had a slightly higher affinity for L-APB, L-homocysteate and NMDA. [3H]Glutamate binding to insect tissues differed in its drug sensitivity from binding to rat brain. Binding to insect membranes was much less sensitive to L-APB, D-APB, APV, homocysteate, L-cysteate, quisqualate and ibotenate. However, the insect binding site was much more stereoselective for the L than D isomers of glutamate and aspartate, while the rat brain site was more stereoselective for APB. It is suggested that the observed [3H]glutamate binding to insect tissue is not to NMDA or kainate receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Receptor turnover and the action of 5-hydroxytryptamine on the salivary glands of the blowfly Calliphora erythrocephala, the housefly Musca domestica and frog skin epithelium

1. Continual stimulation of frog skin epithelium and the salivary glands of the insects Calliphora and Musca with 5-hydroxytryptamine (5-HT) leads to desensitisation, i.e. the tissue fails to respond to the application of further 5-HT. 2. Incubation of desensitised frog skin and Musca salivary glands with either N-acetyl neuraminic acid or inositol partially restored the 5-HT responses whilst incubation with a combination of N-acetyl neuraminic acid and inositol gave additive effects on the recovery of the 5-HT responses. 3. Incubation of desensitised salivary glands of Calliphora with inositol totally restored the 5-HT response whilst incubation with N-acetyl neuraminic acid had no effect. 4. It is concluded that desensitisation involves depletion of secondary messenger from the tissues coupled with receptor degradation and that considerable differences exist in the turnover of 5-HT receptors, the receptors in Musca salivary glands being highly labile, those in Calliphora salivary glands highly stable and those of frog skin epithelium being intermediate in their stability.

Effects of ambient temperature on free radical generation, antioxidant defenses and life span in the adult housefly, Musca domestica

Life spans of poikilotherms like the housefly are shortened by elevation of ambient temperature. The objective of this study was to examine the possible involvement of active oxygen species in temperature induced life-shortening of the adult male housefly. Effects of varied ambient temperature, 20 degrees C and 28 degrees C, on life span, cyanide-resistant respiration, H2O2 concentration, superoxide dismutase (SOD) and catalase activities and glutathione (GSH) concentration were examined. Average life span of flies raised at 28 degrees C was about 52% lower than those raised at 20 degrees C. Rate of cyanide-resistant respiration, an indicator of oxygen free radical generation, was higher in flies raised at 28 degrees C, whereas steady-state concentration of H2O2 was decreased at this temperature. Catalase activity and GSH concentration were lower at 28 degrees C while SOD activity was unaffected by the ambient temperature. Results of this study suggest that life-shortening effects of elevated ambient temperature may be due, in part, to increased oxidative stress.

Relationship between life expectancy, endogenous antioxidants and products of oxygen free radical reactions in the housefly, Musca domestica

The general objective of this study was to identify biochemical correlates of life expectancy in the adult male housefly. All houseflies lose flying ability prior to death, whereby, in an aging population, shorter-lived flies can be identified as flightless 'crawlers' from their longer-lived cohorts, the 'fliers'; the average lifespan of crawlers is about one-third shorter than the fliers. Neither crawlers nor fliers exhibited any physical damage to their chemoreceptive tarsi, thereby ruling out starvation as a probable cause of death. Levels of antioxidant defenses (superoxide dismutase, catalase and glutathione) and products of oxygen free radical reactions (inorganic peroxides and thiobarbituric acid [TBA]-reactants) were compared between crawlers and fliers. The fliers showed higher superoxide dismutase and catalase activities and glutathione concentration than crawlers, whereas, the amount of inorganic peroxides (H2O2) and TBA-reactants was higher in the crawlers than in fliers. Results of this study demonstrate, for the first time, that longer life expectancy of organisms belonging to the same cohort group is associated with relatively higher levels of antioxidants and lower concentrations of products of oxygen free radical reactions.

Effects of increased lifespan on chromatin condensation in the adult male housefly

Analysis of the chromatin condensation pattern in optic lobe nuclei from the adult male housefly has shown significant differences in males from a long lived, low activity (LA) group as compared to a short lived, high activity (HA) group. The rate of chromatin condensation in the LA group was very much less than that observed in the HA group, leaving the nuclei from the former group in a permanently lowered condensation state. Moreover, a detailed comparison of the amount and spatial distribution of a single high density chromatin component (HDC) suggests that the low activity conditions not only lowers the rate of chromatin condensation but also alters the normal program controlling this process. Linear discriminant analysis showed that a consistently higher percentage of nuclei from the LA group, as compared to the HA group, could be classified with a 1-day-old model derived from the HA group. These results are discussed with respect to environmental influences on lifespan and are compared to the response of lipofuscin accumulation in low activity male houseflies.

Iron induces oxidative stress and may alter the rate of aging in the housefly, Musca domestica

Iron is known to play a catalytic role in the generation of oxygen free radicals in vitro. The present study was conducted in order to determine the in vivo effects of iron intake. Administration of 2 mM ferrous chloride to adult male houseflies in their drinking water significantly shortened their life span, increased the concentration of inorganic peroxides and chloroform-soluble fluorescent material, and stimulated the activity of catalase. Levels of superoxide dismutase activity, glutathione and oxygen utilization were unaffected. Overall, these results indicate that iron causes oxidative stress in vivo and may influence the rate of aging.

Effects of exogenous antioxidants on the levels of endogenous antioxidants, lipid-soluble fluorescent material and life span in the housefly, Musca domestica

Effects of exogenous antioxidant administration (0.5% and 2% ascorbate, beta-carotene and alpha-tocopherol in sucrose) on life-span, metabolic rate, activities of superoxide dismutase and catalase, levels of glutathione, inorganic peroxides and chloroform-soluble fluorescent material (lipofuscin) were examined in adult male houseflies. Administration of antioxidants at a level of 0.5% did not affect life-span, whereas, 2% ascorbate and alpha-tocopherol decreased average life-span. Metabolic rate of flies was unaffected, except by 2% ascorbate, which caused a decrease. Superoxide dismutase activity was depressed by 2% ascorbate at all ages, and by beta-carotene and alpha-tocopherol in older flies. Catalase activity was unaffected except by alpha-tocopherol at younger ages. Glutathione concentration was decreased by ascorbate and beta-carotene at both concentrations administered. Inorganic peroxides (H2O2) were increased by 2% beta-carotene and alpha-tocopherol. Only high concentrations of ascorbate and beta-carotene decreased the level of soluble fluorescent material. Results suggest that administration of exogenous antioxidants causes a compensatory depression of endogenous defenses.

Chlorocyclohexane insecticides and male medfly attractants: similar stereospecificity for neuroactivity and interactions with a housefly [35S]t-butylbicyclophosphorothionate binding site

[35S]t-Butylbicyclophosphorothionate [( 35S]TBPS) undergoes saturable specific binding to a membrane preparation from housefly thoraxes and abdomens with apparent Kd and Bmax values at equilibrium of 0.17 microM and 2.2 pmol/mg protein at 20 degrees C. Lindane is more potent than three other isomers of hexachlorocyclohexane as a toxicant for houseflies and in displacing [35S]TBPS from this housefly membrane preparation. This correlation of similar stereospecificity for neuroactivity and interaction with the TBPS receptor extends to the Mediterranean fruit fly male attractant trimedlure and its components and analogs. The relative attractancy of t-butyl cis-4-chloro-trans-2-methylcyclohexanecarboxylate and of three less active isomers of this trans-chlorocyclohexane-carboxylate parallel their potency in the [35S]TBPS binding assay. With both trimedlure and the related cyclohexene attractant siglure the trans-isomers are more potent than the cis-isomers as attractants and in displacing [35S]TBPS. Scatchard analyses indicate that lindane binds at the same site as [35S]TBPS. The hexachlorocyclohexane isomers and trimedlure components are much more potent inhibitors with membrane preparations from houseflies than from rat brain. The housefly TBPS receptor possibly serves as a model for the primary target sites, thereby suggesting that both the insecticide and the attractant may interact with some component of the putative GABAergic nervous or neuromuscular system.

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-related chromatin condensation in flight muscle nuclei of the adult male housefly, Musca domestica

Computer analysis of indirect flight muscle nuclei from the adult male housefly, M. domestica, has shown significant change with age in the chromatin condensation pattern. The pattern was analyzed by examining low, medium, and high density chromatin components (LDC, MDC, HDC). No significant change occurred in HDC with age, and the amount and distribution of LDC and MDC remain relatively stable between Day 1 and Day 4 post-eclosion. However, the analysis showed a significant increase in the amount of MDC with a corresponding decrease in the amount of LDC between Day 4 and Day 14. This exchange was accompanied by a significant redistribution of both components. These results are discussed with reference to the biochemical and ultrastructural profile of the flight muscle with age, and to age-related changes in the condensation pattern of specific brain and Malpighian tubule nuclei described earlier.