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Alzheimer's disease (AD) patients present with symptoms such as impairment of insulin signaling, chronic inflammation, and oxidative stress. Furthermore, there are comorbidities associated with AD progression. For example, osteoporosis is common with AD wherein patients exhibit reduced mineralization and a risk for fragility fractures. However, there is a lack of understanding on the effects of AD on bone beyond loss of bone density. To this end, we investigated the effects of AD on bone quality using the 5XFAD transgenic mouse model in which 12-month-old 5XFAD mice showed accumulation of amyloid-beta (Aβ42) compared with wild-type (WT) littermates (n = 10/group; 50% female, 50% male). Here, we observed changes in cortical bone but not in cancellous bone quality. Both bone mass and bone quality, measured in femoral samples using imaging (micro-CT, confocal Raman spectroscopy, X-ray diffraction [XRD]), mechanical (fracture tests), and chemical analyses (biochemical assays), were altered in the 5XFAD mice compared with WT. Micro-CT results showed 5XFAD mice had lower volumetric bone mineral density (BMD) and increased endocortical bone loss. XRD results showed decreased mineralization with smaller mineral crystals. Bone matrix compositional properties, from Raman, showed decreased crystallinity along with higher accumulation of glycoxidation products and glycation products, measured biochemically. 5XFAD mice also demonstrated loss of initiation and maximum toughness. We observed that carboxymethyl-lysine (CML) and mineralization correlated with initiation toughness, whereas crystal size and pentosidine (PEN) correlated with maximum toughness, suggesting bone matrix changes predominated by advanced glycation end products (AGEs) and altered/poor mineral quality explained loss of fracture toughness. Our findings highlight two pathways to skeletal fragility in AD through alteration of bone quality: (i) accumulation of AGEs; and (ii) loss of crystallinity, decreased crystal size, and loss of mineralization. We observed that the accumulation of amyloidosis in brain correlated with an increase in several AGEs, consistent with a mechanistic link between elevated Aβ42 levels in the brain and AGE accumulation in bone. © 2022 American Society for Bone and Mineral Research (ASBMR)., (© 2022 American Society for Bone and Mineral Research (ASBMR).)

Circadian disruption resulting from exposure to irregular light-dark patterns and sleep deprivation has been associated with beta amyloid peptide (Aβ) aggregation, which is a major event in Alzheimer's disease (AD) pathology. We exposed 5XFAD mice and littermate controls to dim-light vs. bright-light photophases to investigate the effects of altering photophase strength on AD-associated differences in cortical Aβ42 levels, wheel-running activity, and circadian free-running period (tauDD). We found that increasing light levels significantly reduced cortical Aβ42 accumulation and activity levels during the light phase of the light:dark cycle, the latter being consistent with decreased sleep fragmentation and increased sleep duration for mice exposed to the more robust light-dark pattern. No significant changes were observed for tauDD. Our results are consistent with circadian pacemaker period being relatively unaffected by Aβ pathology in AD, and with reductions in cortical Aβ loads in AD through tailored lighting interventions.

Female vinegar flies (Drosophila melanogaster) preferentially oviposit eggs on oviposition substrates that decrease larval foraging costs. We tested whether female D. melanogaster would avoid oviposition substrates containing lead (Pb 2+ ), which could potentially decrease offspring fitness. Wild type D. melanogaster were reared on control or Pb-treated medium from egg stage to adulthood and tested for differences in oviposition substrate preference, fecundity (number of eggs laid) and Pb accumulation. Control females laid a significantly lower proportion of eggs on Pb-treated substrates than Pb-treated females. Pb-treated females laid significantly more eggs than control females. Pb-treated adults accumulated significantly more Pb than control-treated adults. These results indicate that Pb exposure disrupts normal oviposition avoidance behaviors, which could increase larval foraging costs for larval offspring. These factors could induce population declines and have cascading implications for the ecosystem.

We aimed to identify genetic variation in the response of reproductive behaviors to lead (Pb 2+ ) exposure. We reared a subset of the Drosophila Genetic Reference Panel (DGRP) inbred lines on control or Pb-treated (500 μM PbAc) medium and tested for differences in copulation latency, copulation duration, and fecundity. Pb exposure decreased fecundity (p < 0.05) and increased copulation duration (p < 0.05) across DGRP lines. We found intraspecific genetic variation in latency, duration, and fecundity in both control and Pb-treated flies, with heritability ranging from 0.45 to 0.80. We found a significant genotype-by-environment interaction for copulation duration (p < 0.05). Genetic correlation matrices revealed significant genetic variation in common between control and Pb-treated flies for each trait (p < 0.05). Our results indicate that intraspecific genetic variation plays a role in Pb susceptibility and emphasize the importance of considering the impacts of variation in susceptibility to Pb pollution.

We investigated effects of apterous mutation ap 56f on circadian locomotor activity, eclosion rhythms, and transcript levels of period and timeless in Drosophila . We investigated circadian locomotor activity and eclosion rhythms in ap 56f and wild-type flies, their F1 and F2 offspring, and wingless vestigial mutants and show that ap 56f disrupts circadian locomotor rhythms in a genetically recessive manner, that is not caused by the absence of wings. The ap blt strain also showed impaired circadian activity rhythms, providing independent evidence for a significant role of apterous in circadian locomotor rhythm expression. The ap 56f mutation did not disrupt a circadian eclosion rhythm or rhythmic expression of the period and timeless clock genes, indicating that apterous is not essential for circadian clock function, but is necessary for coupling locomotor activity to a circadian clock. Timeless transcription was reduced in ap 56f flies in 12:12 LD, suggesting that apterous may modulate core clock gene expression.

Mitochondrial dysfunction plays a significant role in neurodegenerative disease including ataxias and other movement disorders, particularly those marked by progressive degeneration in the cerebellum. In this study, we investigate the role of mitochondrial oxidative phosphorylation (OXPHOS) deficits in cerebellar tissue of a Purkinje cell-driven spinocerebellar ataxia type 1 (SCA1) mouse. Using RNA sequencing transcriptomics, OXPHOS complex assembly analysis and oxygen consumption assays, we report that in the presence of mutant polyglutamine-expanded ataxin-1, SCA1 mice display deficits in cerebellar OXPHOS complex I (NADH-coenzyme Q oxidoreductase). Complex I genes are upregulated at the time of symptom onset and upregulation persists into late stage disease; yet, functional assembly of complex I macromolecules are diminished and oxygen respiration through complex I is reduced. Acute treatment of postsymptomatic SCA1 mice with succinic acid, a complex II (succinate dehydrogenase) electron donor to bypass complex I dysfunction, ameliorated cerebellar OXPHOS dysfunction, reduced cerebellar pathology and improved motor behavior. Thus, exploration of mitochondrial dysfunction and its role in neurodegenerative ataxias, and warrants further investigation.

We examined accumulation, sequestration, elimination, and genetic variation for lead (Pb) loads within and between generations of Drosophila melanogaster. Flies were reared in control or leaded medium at various doses and tested for their Pb loads at different stages of development (larvae, eclosion, newly-eclosed adults, and mature adults). Pb loads were tested using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). We found that D. melanogaster readily accumulated Pb throughout their lifespan and the levels of accumulation increased with Pb exposure in the medium. Wandering third-instar larvae accumulated more Pb than mature adults; this phenomenon may be due to elimination of Pb in the pupal cases during eclosion and/or depuration in adults post-eclosion. The accumulated Pb in mature adults was not transferred to F 1 mature adult offspring. Using a set of recombinant inbred strains, we identified a quantitative trait locus for adult Pb loads and found that genetic variation accounted for 34% of the variance in Pb load. We concluded that D. melanogaster is a useful model organism for evaluating changes in Pb loads during development, as well as between generations. Furthermore, we found that genetic factors can influence Pb loads; this provides an essential foundation for evaluating phenotypic variation induced by the toxic effects of Pb., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Obesity is a major public health problem that is highly associated with insulin resistance and type 2 diabetes, two conditions associated with circadian disruption. To date, dieting is one of the only interventions that result in substantial weight loss, but restricting caloric intake is difficult to maintain long-term. The use of artificial sweeteners, particularly in individuals that consume sugar sweetened beverages (energy drinks, soda), can reduce caloric intake and possibly facilitate weight loss. The purpose of the present study was to examine the effects of the artificial sweetener, rebaudioside A (Reb-A), on circadian rhythms, in vivo insulin action, and the susceptibility to diet-induced obesity. Six month old male C57BL/6 mice were assigned to a control or Reb-A (0.1% Reb-A supplemented drinking water) group for six months. Circadian wheel running rhythms, body weight, caloric intake, insulin action, and susceptibility to diet-induced obesity were assessed. Time of peak physical activity under a 12:12 light-dark (LD) cycle, mean activity levels, and circadian period in constant dark were not significantly different in mice that consumed Reb-A supplemented water compared to normal drinking water, indicating that circadian rhythms and biological clock function were unaltered. Although wheel running significantly reduced body weight in both Reb-A and control mice (P = 0.0001), consuming Reb-A supplemented water did not alter the changes in body weight following wheel running (P = 0.916). In vivo insulin action, as assessed by glucose, insulin, and pyruvate tolerance tests, was not different between mice that consumed Reb-A treated water compared to normal drinking water. Finally, Reb-A does not appear to change the susceptibility to diet-induced obesity as both groups of mice gained similar amounts of body weight when placed on a high fat diet. Our results indicate that consuming Reb-A supplemented water does not promote circadian disruption, insulin resistance, or obesity.

Anthropogenic pollutants have the potential to disrupt reproductive strategies. Little is known about how lead (Pb 2+ ) exposure disrupts individual-level responses in reproductive behaviors, which are important for fitness. Drosophila melanogaster was used as a model system to determine the effects of: 1) developmental lead exposure on pre-mating reproductive behaviors (i.e., mate preference), and 2) lead exposure and mating preferences on fitness in the F 0 parental generation and F 1 un-exposed offspring. Wild-type strains of D. melanogaster were reared from egg stage to adulthood in control or leaded medium (250 μM PbAc) and tested for differences in: mate preference, male song performance, sex pheromone expression, fecundity, mortality, and body weight. F 0 leaded females preferentially mated with leaded males (i.e., asymmetrical positive assortative mating) in 2-choice tests. This positive assortative mating was mediated by the females (and not the males) and was dependent upon context and developmental exposure to Pb. Neither the courtship song nor the sex pheromone profile expressed by control and leaded males mediated the positive assortative mating in leaded females. Leaded females did not incur a fitness cost in terms of reduced fecundity, increased mortality, or decreased body weight by mating with leaded males. These results suggest that sublethal exposure to lead during development can alter mate preferences in adults, but not fitness measures once lead exposure has been removed. We suggest that changes in mate preference may induce fitness costs, as well as long-term population and multi-generational implications, if pollution is persistent in the environment.

Circadian behavioural deficits, including sleep irregularity and restlessness in the evening, are a distressing early feature of Alzheimer's disease (AD). We have investigated these phenomena by studying the circadian behaviour of transgenic Drosophila expressing the amyloid beta peptide (Aβ). We find that Aβ expression results in an age-related loss of circadian behavioural rhythms despite ongoing normal molecular oscillations in the central clock neurons. Even in the absence of any behavioural correlate, the synchronised activity of the central clock remains protective, prolonging lifespan, in Aβ flies just as it does in control flies. Confocal microscopy and bioluminescence measurements point to processes downstream of the molecular clock as the main site of Aβ toxicity. In addition, there seems to be significant non-cell-autonomous Aβ toxicity resulting in morphological and probably functional signalling deficits in central clock neurons.

Alcohol consumption causes disruptions in a variety of daily rhythms, including the circadian free-running rhythm. A previous study conducted in our laboratories has shown that larval ethanol exposure alters the free-running period in adult Canton-S Drosophila melanogaster. Few studies, however, have explored the effect of alcohol exposure on organisms exhibiting circadian periods radically different than (normal) 24-h. We reared Canton-S, period long, and period short Drosophila melanogaster larvae on 10%-ethanol supplemented food, and assessed their adult free-running locomotor activity and period transcript at ZT 12. We demonstrate that in Canton-S larval ethanol exposure shortens the adult free-running locomotor activity but does not significantly alter period mRNA levels at ZT 12. Period long mutants exposed to larval ethanol had significantly shortened adult free-running locomotor activity rhythms and decreased period mRNA levels, while period short mutants lengthened their free-running rhythm and showed increased period mRNA levels at ZT 12 after being exposed to larval ethanol. These results indicate that the effects of ethanol on the circadian clock might depend upon the baseline circadian period of the organism or that period mutant gene expression is sensitive to developmental ethanol treatment., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Drosophila melanogaster is an excellent model animal for studying the neurotoxicology of lead. It has been known since ancient Roman times that long-term exposure to low levels of lead results in behavioral abnormalities, such as what is now known as attention deficit hyperactivity disorder (ADHD). Because lead alters mechanisms that underlie developmental neuronal plasticity, chronic exposure of children, even at blood lead levels below the current CDC community action level (10 μg/dl), can result in reduced cognitive ability, increased likelihood of delinquency, behaviors associated with ADHD, changes in activity level, altered sensory function, delayed onset of sexual maturity in girls, and changes in immune function. In order to better understand how lead affects neuronal plasticity, we will describe recent findings from a Drosophila behavioral genetics laboratory, a Drosophila neurophysiology laboratory, and a Drosophila quantitative genetics laboratory who have joined forces to study the effects of lead on the Drosophila nervous system. Studying the effects of lead on Drosophila nervous system development will give us a better understanding of the mechanisms of Pb neurotoxicity in the developing human nervous system.

Alcohol consumption causes disruptions in a variety of daily rhythms, including the sleep-wake cycle. Few studies have explored the effect of alcohol exposure only during developmental stages preceding maturation of the adult circadian clock, and none have examined the effects of alcohol on clock function in Drosophila. This study investigates developmental and behavioral correlates between larval ethanol exposure and the adult circadian clock in Drosophila melanogaster, a well-established model for studying circadian rhythms and effects of ethanol exposure. We reared Drosophila larvae on 0%, 10%, or 20% ethanol-supplemented food and assessed effects upon eclosion and the free-running period of the circadian rhythm of locomotor activity. We observed a dose-dependent effect of ethanol on period, with higher doses resulting in shorter periods. We also identified the third larval instar stage as a critical time for the developmental effects of 10% ethanol on circadian period. These results demonstrate that developmental ethanol exposure causes sustainable shortening of the adult free-running period in Drosophila melanogaster, even after adult exposure to ethanol is terminated, and suggests that the third instar is a sensitive time for this effect.

During puberty, humans develop a later chronotype, exhibiting a phase-delayed daily rest/activity rhythm. The purpose of this study was to determine: 1) whether similar changes in chronotype occur during puberty in a laboratory rodent species, 2) whether these changes are due to pubertal hormones affecting the circadian timekeeping system. We tracked the phasing and distribution of wheel-running activity rhythms during post-weaning development in rats that were gonadectomized before puberty or left intact. We found that intact peripubertal rats had activity rhythms that were phase-delayed relative to adults. Young rats also exhibited a bimodal nocturnal activity distribution. As puberty progressed, bimodality diminished and late-night activity phase-advanced until it consolidated with early-night activity. By late puberty, intact rats showed a strong, unimodal rhythm that peaked at the beginning of the night. These pubertal changes in circadian phase were more pronounced in males than females. Increases in gonadal hormones during puberty partially accounted for these changes, as rats that were gonadectomized before puberty demonstrated smaller phase changes than intact rats and maintained ultradian rhythms into adulthood. We investigated the role of photic entrainment by comparing circadian development under constant and entrained conditions. We found that the period (τ) of free-running rhythms developed sex differences during puberty. These changes in τ did not account for pubertal changes in entrained circadian phase, as the consolidation of activity at the beginning of the subjective night persisted under constant conditions in both sexes. We conclude that the circadian system continues to develop in a hormone-sensitive manner during puberty., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Environmental exposure to Pb(2+) affects hormone-mediated responses in vertebrates. To help establish the fruit fly, Drosophila melanogaster, as a model system for studying such disruption, we describe effects of Pb(2+) on hormonally regulated traits. These include duration of development, longevity, females' willingness to mate, fecundity and adult locomotor activity. Developmental Pb(2+) exposure has been shown to affect gene expression in a specific region of the Drosophila genome (approximately 122 genes) involved in lead-induced changes in adult locomotion and to affect regulation of intracellular calcium levels associated with neuronal activity at identified synapses in the larval neuromuscular junction. We suggest ways in which Drosophila could become a new model system for the study of endocrine disruptors at genetic, neural and behavioral levels of analysis, particularly by use of genomic methods. This will facilitate efforts to distinguish between behavioral effects of Pb(2+) caused by direct action on neural mechanisms versus effects of Pb(+2) on behavior mediated through endocrine disruption., (2009 Elsevier Inc. All rights reserved.)

The genetics of gene expression in recombinant inbred lines (RILs) can be mapped as expression quantitative trait loci (eQTLs). So-called "genetical genomics" studies have identified locally acting eQTLs (cis-eQTLs) for genes that show differences in steady-state RNA levels. These studies have also identified distantly acting master-modulatory trans-eQTLs that regulate tens or hundreds of transcripts (hotspots or transbands). We expand on these studies by performing genetical genomics experiments in two environments in order to identify trans-eQTL that might be regulated by developmental exposure to the neurotoxin lead. Flies from each of 75 RIL were raised from eggs to adults on either control food (made with 250 microM sodium acetate), or lead-treated food (made with 250 microM lead acetate, PbAc). RNA expression analyses of whole adult male flies (5-10 days old) were performed with Affymetrix DrosII whole genome arrays (18,952 probesets). Among the 1389 genes with cis-eQTL, there were 405 genes unique to control flies and 544 genes unique to lead-treated ones (440 genes had the same cis-eQTLs in both samples). There are 2396 genes with trans-eQTL which mapped to 12 major transbands with greater than 95 genes. Permutation analyses of the strain labels but not the expression data suggests that the total number of eQTL and the number of transbands are more important criteria for validation than the size of the transband. Two transbands, one located on the 2nd chromosome and one on the 3rd chromosome, co-regulate 33 lead-induced genes, many of which are involved in neurodevelopmental processes. For these 33 genes, rather than allelic variation at one locus exerting differential effects in two environments, we found that variation at two different loci are required for optimal effects on lead-induced expression.

Considerable progress has been made over the past couple of decades concerning the molecular bases of neurobehavioral function and dysfunction. The field of neurobehavioral genetics is becoming mature. Genetic factors contributing to neurologic diseases such as Alzheimer's disease have been found and evidence for genetic factors contributing to other diseases such as schizophrenia and autism are likely. This genetic approach can also benefit the field of behavioral neurotoxicology. It is clear that there is substantial heterogeneity of response with behavioral impairments resulting from neurotoxicants. Many factors contribute to differential sensitivity, but it is likely that genetic variability plays a prominent role. Important discoveries concerning genetics and behavioral neurotoxicity are being made on a broad front from work with invertebrate and piscine mutant models to classic mouse knockout models and human epidemiologic studies of polymorphisms. Discovering genetic factors of susceptibility to neurobehavioral toxicity not only helps identify those at special risk, it also advances our understanding of the mechanisms by which toxicants impair neurobehavioral function in the larger population. This symposium organized by Edward Levin and Annette Kirshner, brought together researchers from the laboratories of Michael Aschner, Douglas Ruden, Ulrike Heberlein, Edward Levin and Kathleen Welsh-Bohmer conducting studies with Caenorhabditis elegans, Drosophila, fish, rodents and humans studies to determine the role of genetic factors in susceptibility to behavioral impairment from neurotoxic exposure.

We developed Drosophila melanogaster as a model to study correlated behavioral, neuronal and genetic effects of the neurotoxin lead, known to affect cognitive and behavioral development in children. We showed that, as in vertebrates, lead affects both synaptic development and complex behaviors (courtship, fecundity, locomotor activity) in Drosophila. By assessing differential behavioral responses to developmental lead exposure among recombinant inbred Drosophila lines (RI), derived from parental lines Oregon R and Russian 2b, we have now identified a genotype by environment interaction (GEI) for a behavioral trait affected by lead. Drosophila Activity Monitors (TriKinetics, Waltham, MA), which measure activity by counting the number of times a single fly in a small glass tube walks through an infrared beam aimed at the middle of the tube, were used to measure activity of flies, reared from eggs to 4 days of adult age on either control or lead-contaminated medium, from each of 75 RI lines. We observed a significant statistical association between the effect of lead on Average Daytime Activity (ADA) across lines and one marker locus, 30AB, on chromosome 2; we define this as a Quantitative Trait Locus (QTL) associated with behavioral effects of developmental lead exposure. When 30AB was from Russian 2b, lead significantly increased locomotor activity, whereas, when 30AB was from Oregon R, lead decreased it. 30AB contains about 125 genes among which are likely "candidate genes" for the observed lead-dependent behavioral changes. Drosophila are thus a useful, underutilized model for studying behavioral, synaptic and genetic changes following chronic exposure to lead or other neurotoxins during development.

In humans, anabolic androgenic steroid (AAS) use has been associated with hyperactivity and disruption of circadian rhythmicity. We used an animal model to determine the impact of AAS on the development and expression of circadian function. Beginning on day 68 gonadally intact male rats received testosterone, nandrolone, or stanozolol via constant release pellets for 60 days; gonadally intact controls received vehicle pellets. Wheel running was recorded in a 12:12 LD cycle and constant dim red light (RR) before and after AAS implants. Post-AAS implant, circadian activity phase, period and mean level of wheel running wheel activity were compared to baseline measures. Post-AAS phase response to a light pulse at circadian time 15 h was also tested. To determine if AAS differentially affects steroid receptor coactivator (SRC) expression we measured SRC-1 and SRC-2 protein in brain. Running wheel activity was significantly elevated by testosterone, significantly depressed by nandrolone, and unaffected by stanozolol. None of the AAS altered measures of circadian rhythmicity or phase response. While SRC-1 was unaffected by AAS exposure, SRC-2 was decreased by testosterone in the hypothalamus. Activity levels, phase of peak activity and circadian period all changed over the course of development from puberty to adulthood. Development of activity was clearly modified by AAS exposure as testosterone significantly elevated activity levels and nandrolone significantly suppressed activity relative to controls. Thus, AAS exposure differentially affects both the magnitude and direction of developmental changes in activity levels depending in part on the chemical composition of the AAS.

Anabolic androgenic steroids (AAS) have been linked to indiscriminant and unprovoked aggression and violence. We employed a brief tail pinch to examine the effects of different AAS on intermale aggression in gonadally intact male rats in response to a mild physical provocation. Animals received 5 mg/kg testosterone propionate (TP), nandrolone (ND), or stanozolol (ST) 5 days/week. Controls received vehicle injections. After 12 weeks, rats were tested for aggression while treatments continued. Animals were paired with either gonadally intact or castrated opponents and were tested in the subject rat's home cage, the opponents's home cage, and a neutral cage. Aggression was tested during tail pinch of the subject rat and during tail pinch of the opponent rat. In TP-treated males, tail pinch significantly enhanced aggression in all social and environmental conditions compared to intact controls. TP treatment also significantly enhanced aggression when the opponents were tail pinched. Tail pinch did not increase aggression in ND-treated males, and aggression was significantly lower than controls in ST-treated males. As expected, cell nuclear androgen receptor binding was significantly elevated by the high dose of TP. Our results show that while AAS alone does not induce the indiscriminate and unprovoked aggression characteristic of 'roid rage, TP heightens the animals sensitivity to

This study examined the effects of anabolic androgenic steroids (AAS) on aggression under different social and environmental conditions. Three AAS were tested in gonadally intact male rats: testosterone propionate (TP), nandrolone (ND), and stanozolol (ST). Doses of 5 mg/kg were given 5 times/week, with gonadally intact controls receiving vehicle only (propylene glycol). Animals received six weekly tests under each condition in a counterbalanced order. Results show that the three AAS differed in their ability to elicit aggression. Males receiving TP were more aggressive than controls, ND males were similar to controls, and ST males were less aggressive than controls. In the social and environmental provocation tests TP-treated males were more aggressive than other groups, but were able to discriminate between intact and castrated opponents and between their home cage and a neutral cage. In the environmental provocation test, TP males were also more aggressive against opponents when tested in the opponent's home cage. It is suggested that chronic exposure to high levels of TP does not eliminate the ability to discriminate between social or environmental cues, as might be expected if it induces a " 'roid rage." However, TP does increase the likelihood that the animal will respond with aggression/dominance in a provoking situation. All three AAS variably affected serum testosterone and LH levels, as well as testes, seminal vesicle, and prostate weights. No effect on body weight was observed., (Copyright 2001 Academic Press.)

The timeless (tim) gene is essential for circadian clock function in Drosophila melanogaster. A putative mouse homolog, mTimeless (mTim), has been difficult to place in the circadian clock of mammals. Here we show that mTim is essential for embryonic development, but does not have substantiated circadian function.

Wheel running was monitored in B x D recombinant inbred (RI) mice under dark-dark (DD) conditions, and the mean circadian period was calculated for each strain. There were significant differences for this trait among B x D recombinant inbred strains (p < .0001) and a narrow-sense heritability of 21%. Analysis of strain means and variances indicates that at least four segregating loci contribute to the genetic variance for the free-running circadian period in this population. Correlation of the strain means for the circadian period of wheel running for each RI strain against the distribution of markers at over 1500 loci along the mouse genome identified a number of provisional quantitative trait loci (QTL). There were provisional QTL for wheel running at p < .001 on chromosome 11 and at p < .01 on chromosomes 1, 6, 9, 17, and 19. Most were in agreement with a second analysis done under similar conditions.

Seven isogenic strains of Drosophila melanogaster were assayed for oviposition preference on food with phenylthiocarbamide (PTC) versus plain food. There was significant variation among strains for the percentage of eggs oviposited on each medium, ranging from 70 +/- 4% (SE) preference for plain food to no significant preference. Reciprocal hybrid, backcross, and F2 generations derived from two extreme parent strains revealed significant additive and nonadditive genetic variation but no evidence of maternal, paternal, or sex-chromosome effects.

The effect of aging on the free-running period (TauDD) of a circadian rhythm for wheel-running activity was observed in two inbred strains (DBA/ 2J and C57BL/6J) and one outbred strain (Tac: (SW)fBR) of laboratory mice (Mus musculus). TauDD in the DBA and C57 mice was monitored at approximately age 100 days and age 300 days. TauDD in the outbred strain was monitored at approximately age 100 days and age 600 days. TauDD increased with age in all three strains. Most studies of age effects in rodent species have shown a shortening of TauDD with age, with th exception of the C57BL inbred mice. These results show that the lengthening of TauDD with age in laboratory mice is not limited to the C57BL strain and may be a general characteristic of this species, in contrast to other rodent species examined.

The locomotor activity of male mice (Mus musculus) was monitored by infrared photo-electric beams under three lighting regimens: LD (12 h of light and 12 h of dark), DD (constant dark), and LL (constant broad-spectrum light, 10 lux). Circadian period of locomotor activity (tau) was compared among 3 inbred strains of mice, C57BL/6J (B6), BALB/c (C), and DBA/2J (D2), and 26 recombinant inbred strains B x D (B6 x D2). The tau under both continuous low-intensity light and continuous darkness varied significantly among strains. Under DD the mean tau was 23.8 h for B6, 23.7 h for D2, and 23.6 h for C. Under LL the mean tau was 25.1 h for B6, 23.9 h for D2, and 25.5 h for C. Frequency histograms of the mean tau of 26 B x D RI mouse strains (three to seven animals per strain) in either DD or LL and the difference between them, delta tau, had distributions which appeared unimodal, suggesting polygenic inheritances. The narrow-sense heritability determined using 26 strains of B x D RI mice was about 55% for tau and about 38% for both tau in LL and delta tau. An estimated four loci contribute to the variance of tau in constant darkness and five to the variance of tau in constant low-intensity light among the strains studied. Quantitative trait locus (QTL) analysis identified several potential genetic loci associated with tau in constant darkness, tau in constant low-intensity light, and delta tau. The associations of highest probability for each of these traits were the D1Nds4 locus (p < .001) on mouse chromosome 1, the D5Ncvs52 locus (p < .05) on mouse chromosome 5, and the Pmv12 locus (p < .01) at 70 cM on mouse chromosome 5, respectively. A QTL identified for tau was associated (p < .05) with the D2NDS1 marker at 45 cM on chromosome 2 near the Ea 6 marker at 46 cM associated (p < .05) with that reported for the period of wheel running activity in seven C x B RI strains (Schwartz, W.J., and Zimmerman, P., J. Neurosci. 10:3685 1990).

Ablation of olfactory bulbs in rats reduced male sexual behavior, and altered the distribution of wheel-running activity between the light and dark phases of a 12:12 LD photoperiod. These effects were partially reversed by the tricyclic antidepressant amitriptyline. Olfactory bulbectomy also altered serotonin metabolism (5-HIAA/5-HT ratio) in the frontal cortex, nucleus accumbens, hippocampus and corpus striatum. These observations support the hypothesis that olfactory bulbectomy in rodents serves as a model of agitated hyposerotonergic depression.

Fluoxetine is a potent and specific serotonin re-uptake inhibitor and an effective antidepressant drug. Male mice were treated with either fluoxetine (8 mg/kg body weight per day) or saline. Wheel running activity was monitored for 2 weeks in a 12:12 LD cycle followed by 2 weeks in constant darkness (DD). Fluoxetine significantly shortened free-running circadian period for wheel running activity (23.93 +/- 0.08 h for fluoxetine treated mice versus 24.17 +/- 0.07 h for saline treated mice; p less than 0.03). These results are consistent with a role for serotonin in the regulation of circadian period in mice.

For further characterization of the olfactory bulb's role in the medication of chronobiological phenomena, we examined basal cyclic- 3',5'-adenosine monophosphate (cAMP) levels in the suprachiasmatic nuclei (SCN) and lateral hippocampus (LHIP) following bilateral olfactory bulbectomy (OBX) to assess the effects of olfactory bulb removal on the biological clock. Two groups of adult Long-Evans rats underwent OBX or sham control surgery (SHAM). Eight weeks postoperative, the animals were decapitated at the time of maximal cAMP accumulation (circadian time 9-11 h), brains were removed, frozen in liquid nitrogen, and sectioned on a cryostat. Individual brain nuclei (SCN and LHIP) were microdissected using the Palkovits punch technique and analyzed by scintillation proximity assay for cAMP. We report a 83.6% increase in basal cAMP levels in the SCN following OBX (OBX = 63.7 pmol cAMP/mg protein, SHAM = 34.7 pmol cAMP/mg protein, p less than 0.01). No significant differences in LHIP cAMP levels were found. This specific increase in SCN cAMP, at the time of maximum cAMP accumulation, may give insight into the biochemical basis for altered activity levels following OBX.

The purpose of the present experiment was to assess the effect of olfactory bulbectomy and ovarian hormones on female sexual motivation. Ovariectomized female rats underwent either bilateral bulbectomy or sham surgery. Females received one of four subthreshold hormone treatments: 0% estradiol (E2) plus 500 micrograms progesterone (P), 100% E2 alone, 10% E2 plus 500 micrograms P, or 100% E2 plus 500 micrograms P. Sexual motivation (as indicated by a female's preference for a sexually active male over a castrated male) and proceptivity (dart and ear wiggling sequences) were measured in a three compartment partner preference apparatus. Sexual receptivity (lordosis) was measured separately in a glass arena with a sexually active male. Results showed that olfactory bulb removal facilitates sexual receptivity and proceptivity in females exposed to 10% or 100% E2 in combination with 500 micrograms P. In contrast, sexual motivation was only demonstrated by olfactory bulbectomized females which received 100% E2 in combination with 500 micrograms P. These findings support the hypothesis that olfactory bulbectomy induces a behavioral hypersensitivity to estrogen, and suggest that sexual motivation is an estrogen-mediated response which requires a higher level of estrogen stimulation than sexual receptivity and proceptivity.

Genetic background variation influencing expression of the Antennapaedia homeotic phenotype was examined by crossing the Antp73b allele of the Antennapaedia locus reciprocally into seven isogenically derived wild type strains of Drosophila melanogaster and their genetically heterogeneous parent strain, Dover. The parent Antp73b strain's Antennapaedia phenotype shows a small patch of untransformed antennal tissue remaining on the homeotic femur. The size of this patch was used as an assay for background variation influencing expression of the Antp73b homeotic mutation. Patch size varied approximately six-fold across the different genetic backgrounds. Effects of maternal parent, sex, and sex-linkage were also observed.

Ablation of mouse olfactory bulbs lengthened the circadian period of wheel-running activity by 43 min and delayed the onset of entrained activity by 108 min. A transient increase in activity during the light phase of the 12:12 h light-dark photoperiod also occurred following surgery. These disruptions suggest that olfactory systems can modulate mammalian circadian rhythms.

Mammalian albinism is known to alter neural pathways, reduce retinal pigment, and affect diverse behaviors. Mammalian circadian rhythms have been shown to depend on visual pathways, respond to light intensity and regulate many behaviors. Here we show that mice homozygous for the recessive albino or pinkeye-dilute mutations display shorter circadian rhythms than pigmented controls. We conclude that these pigment loci, or closely linked loci, influence the expression of circadian rhythms in mice.

Progesterone treatments have been shown to increase nesting levels of isolated female mice. Here we compared the effect of exogenous progesterone on the nesting behavior of C57BL/10Sn female Mus domesticus housed individually to nesting levels of the same mice housed in pairs. Progesterone increased nesting by isolated females but had no significant effect on the nesting scores of the same mice when they were grouped into pairs. The effect of exogenous progesterone on nesting levels in C57BL/10Sn females appears to depend on social circumstances.

Lithium has been shown to lengthen free-running circadian periods in a variety of species. Here we show that lithium carbonate differentially lengthens the free-running period of a circadian wheel running rhythm in BALB/CByJ and C57BL/10Sn inbred mouse strains. This result supports previous evidence that lithium lengthens mammalian circadian rhythms, and also demonstrates that gene differences can mediate individual differences in response to lithium treatment.

Nocturnal animals typically display an increase in the free running period of circadian rhythms in response to light in direct proportion to intensity. Here we show that gene differences among inbred strains of mice (Mus musculus) modify the effect of constant bright light on the free running period of a circadian rhythm for wheel running activity. Individuals with the shortest free running periods in dim red light showed the greatest increases in period following exposure to bright light. These effects may be due to gene-imposed differences in the response of a circadian pacemaker to light, or they may be due to gene-imposed differences in visual system function that alter perception of light intensity.

Genetic correlations measure the extent of pleiotropic effects of polygenes on pairs of characters or the closeness of linkage between sets of loci influencing the traits and held in allelic (gametic) disequilibrium. Their importance for research lies primarily in predicting correlated responses of one trait to selection based on values for another, and secondarily in analyzing the complex organization of biological systems. Genetic correlations appear to limit the rate and set the direction of multivariate evolution. In view of this, efficient methods for estimating genetic correlations may be essential for understanding the role of behavior in adaptation and for predicting behavioral change in evolution. In this paper we present methods for the estimation of genetic correlations from inbred strain comparisons. Estimates from inbred strains are relatively easy to obtain and appear to be valid when compared to those derived from more demanding parent-offspring comparisons and to correlated responses to selection.