Smelling fit: scent marking exposes parasitic infection status in the banded mongoose

Preference for uninfected mates is presumed beneficial as it minimizes one’s risk of contracting an infection and infecting one’s offspring. In avian systems, visual ornaments are often used to indicate parasite burdens and facilitate mate choice. However, in mammals, olfactory cues have been proposed to act as a mechanism allowing potential mates to be discriminated by infection status. The effect of infection upon mammalian mate choice is mainly studied in captive rodents where experimental trials support preference for the odors of uninfected mates and some data suggest scent marking is reduced in individuals with high infection burdens. Nevertheless, whether such effects occur in nonmodel and wild systems remains poorly understood. Here, we investigate the interplay between parasite load (estimated using fecal egg counts) and scent marking behavior in a wild population of banded mongooses Mungos mungo. Focusing on a costly protozoan parasite of the genus Isospora and the nematode worm Toxocara, we first show that banded mongooses that engage in frequent, intensive scent marking have lower Isospora loads, suggesting marking behavior may be an indicator trait regarding infection status. We then use odor presentations to demonstrate that banded mongooses mark less in response to odors of opposite sexed individuals with high Isospora and Toxocara loads. As both of these parasites are known to have detrimental effects upon the health of preweaned young in other species, they would appear key targets to avoid during mate choice. Results provide support for scent as an important ornament and mechanism for advertising parasitic infection within wild mammals

A Theory of Natural Addiction

Economic theories of rational addiction aim to describe consumer behavior in the presence of habit-forming goods. We provide a biological foundation for this body of work by formally specifying conditions under which it is optimal to form a habit. We demonstrate the empirical validity of our thesis with an in-depth review and synthesis of the biomedical literature concerning the action of opiates in the mammalian brain and their eects on behavior. Our results lend credence to many of the unconventional behavioral assumptions employed by theories of rational addiction, including adjacent complementarity and the importance of cues, attention, and self-control in determining the behavior of addicts. We oer evidence for the special case of the opiates that "harmful" addiction is the manifestation of a mismatch between behavioral algorithms encoded in the human genome and the expanded menu of choices faced by consumers in the modern world

Influence of photoperiod and sex on locomotor behavior of meadow voles (Microtus pennsylvanicus) in an automated light-dark 'anxiety' test

This study examined the influence of photoperiod on affective behavior (anxiety) of adult male and female meadow voles (Microtus pennsylvanicus), maintained in either a long or short day photoperiod, when tested in an automated (VersaMax) light-dark test. The light-dark test is based on an innate aversion of rodents to novel, brightly illuminated spaces and has been used with laboratory raised species, such as mice, to assess anxiety and/or fear related behaviors. Male and female meadow voles, housed either in a long day (LD: 16h light) or short day (SD: 8h light) photoperiod, were tested in the light-dark apparatus for 30 min on 3 consecutive days. All animals spent significantly (p<0.001) less time in the brightly lit chamber (900 lux) than in the dark chamber. LD voles, especially females, spent significantly less time in the brightly lit area than did SD voles. Both horizontal and vertical movements occurred less frequently per unit time in the dark area relative to the light, but only in the LD voles. LD female voles were the least active group in the dark area on the first test day but the most active group in the light area, despite spending the least amount of time in this area on the second and third test days. The present results show that LD voles exhibit more anxiety related behaviors in this test situation than do SD voles. LD females avoided the brightly lit area the most, particularly when the apparatus was novel. Thus, both photoperiod and sex influence situation-based anxiety in this species. These findings suggest that meadow voles are an excellent animal model in which to examine the role of gonadal hormones, and their modulation of defence related neural systems, in the induction of anxiety.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83869/1/influence_of_photoperiod_and_sex.pd

Physical cues controlling seasonal immune allocation in a naturally-occurring vertebrate

Seasonal patterns in immunity are frequently observed in vertebrates but are poorly understood. Here we focussed on a natural piscine model, the three-spined stickleback (Gasterosteus aculeatus), and asked how seasonal immune allocation is driven by physical variables (time, light and heat). Using functionally-relevant gene expression metrics as a reporter of seasonal immune allocation we synchronously sampled fish monthly from the wild (two habitats), and from semi-natural outdoors mesocosms (stocked from one of the wild habitats). This was repeated across two annual cycles, with continuous within-habitat monitoring of environmental temperature and implementing a manipulation of temperature in the mesocosms. We also conducted a long-term laboratory experiment, subjecting acclimated wild fish to natural and accelerated (× 2) photoperiodic change at 7 and 15°C. The laboratory experiment demonstrated that immune allocation was independent of photoperiod and only a very modest effect, at most, was controlled by a tentative endogenous circannual rhythm. On the other hand, experimentally-determined thermal effects were able to quantitatively predict much of the summer-winter fluctuation observed in the field and mesocosms. Importantly, however, temperature was insufficient to fully predict, and occasionally was a poor predictor of, natural patterns. Thermal effects can thus be over-ridden by other (unidentified) natural environmental variation and do not take the form of an unavoidable constraint due to cold-blooded physiology. This is consistent with a context-dependent strategic control of immunity in response to temperature variation, and points to the existence of temperature-sensitive regulatory circuits that might be conserved in other vertebrates

Molecular evidence that Heligmosomoides polygyrus from laboratory mice and wood mice are separate species

The gastro-intestinal (GI) nematode Heligmosomoides polygyrus is an important experimental model in laboratory mice and a well-studied parasite of wood mice in the field. Despite an extensive literature, the taxonomy of this parasite in different hosts is confused, and it is unclear whether laboratory and field systems represent the same or different Operational Taxonomic Units (OTUs). Molecular analyses reveal high sequence divergence between H. p. bakeri (laboratory) and H. p. polygyrus (field); 3% difference in the ribosomal DNA Internal Transcribed Spacers (ITS) and 8.6% variation in the more rapidly evolving mitochondrial cytochrome c oxidase I (COI) gene. The COI sequence of U.K. H. p. polygyrus is more similar to H. glareoli from voles than to H. p. bakeri, while a single isolate of H. p. polygyrus from Guernsey confirms the extent of genetic variation between H. p. polygyrus populations. Analysis of molecular variance demonstrated that mtCOI sequence variation is associated primarily with groups with distinct ITS2 sequences, and with host identity, but is not partitioned significantly with a single combined taxon H. polygyrus incorporating European and North American isolates. We conclude therefore that the laboratory OTUshould be raised to the level of a distinct species, as H. bakeri from the laboratory mouse Mus musculus, and we reject the hypothesis that H. bakeri has diverged from H. polygyrus in the recent past following introduction into America. However, we are unable to reject the hypothesis that H. polygyrus and H. bakeri are sister taxa, and it may be that H. polygyrus is polyphyletic or paraphyletic

Exposure to strong static magnetic field slows the growth of human cancer cells in vitro

Proposals to enhance the amount of radiation dose delivered to small tumors with radioimmunotherapy by constraining emitted electrons with very strong homogeneous static magnetic fields has renewed interest in the cellular effects of prolonged exposures to such fields. Past investigations have not studied the effects on tumor cell growth of lengthy exposures to very high magnetic fields. Three malignant human cell lines, HTB 63 (melanoma), HTB 77 IP3 (ovarian carcinoma), and CCL 86 (lymphoma; Raji cells), were exposed to a 7 Tesla uniform static magnetic field for 64 hours. Following exposure, the number of viable cells in each group was determined. In addition, multicycle flow cytometry was performed on all cell lines, and pulsed-field electrophoresis was performed solely on Raji cells to investigate changes in cell cycle patterns and the possibility of DNA fragmentation induced by the magnetic field. A 64 h exposure to the magnetic field produced a reduction in viable cell number in each of the three cell lines. Reductions of 19.04 ± 7.32%, 22.06 ± 6.19%, and 40.68 ± 8.31% were measured for the melanoma, ovarian carcinoma, and lymphoma cell lines, respectively, vs. control groups not exposed to the magnetic field. Multicycle flow cytometry revealed that the cell cycle was largely unaltered. Pulsed-field electrophoresis analysis revealed no increase in DNA breaks related to magnetic field exposure. In conclusion, prolonged exposure to a very strong magnetic field appeared to inhibit the growth of three human tumor cell lines in vitro. The mechanism underlying this effect has not, as yet, been identified, although alteration of cell growth cycle and gross fragmentation of DNA have been excluded as possible contributory factors. Future investigations of this phenomenon may have a significant impact on the future understanding and treatment of cancer. © 1996 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38293/1/2_ftp.pd

Expression of progesterone metabolizing enzyme genes (AKR1C1, AKR1C2, AKR1C3, SRD5A1, SRD5A2) is altered in human breast carcinoma

BACKGROUND: Recent evidence suggests that progesterone metabolites play important roles in regulating breast cancer. Previous studies have shown that tumorous tissues have higher 5α-reductase (5αR) and lower 3α-hydroxysteroid oxidoreductase (3α-HSO) and 20α-HSO activities. The resulting higher levels of 5α-reduced progesterone metabolites such as 5α-pregnane-3,20-dione (5αP) in tumorous tissue promote cell proliferation and detachment, whereas the 4-pregnene metabolites, 4-pregnen-3α-ol-20-one (3αHP) and 4-pregnen-20α-ol-3-one (20αDHP), more prominent in normal tissue, have the opposite (anti-cancer-like) effects. The aim of this study was to determine if the differences in enzyme activities between tumorous and nontumorous breast tissues are associated with differences in progesterone metabolizing enzyme gene expression. METHODS: Semi-quantitative RT-PCR was used to compare relative expression (as a ratio of 18S rRNA) of 5αR type 1 (SRD5A1), 5αR type 2 (SRD5A2), 3α-HSO type 2 (AKR1C3), 3α-HSO type 3 (AKR1C2) and 20α-HSO (AKR1C1) mRNAs in paired (tumorous and nontumorous) breast tissues from 11 patients, and unpaired tumor tissues from 17 patients and normal tissues from 10 reduction mammoplasty samples. RESULTS: Expression of 5αR1 and 5αR2 in 11/11 patients was higher (mean of 4.9- and 3.5-fold, respectively; p < 0.001) in the tumor as compared to the paired normal tissues. Conversely, expression of 3α-HSO2, 3α-HSO3 and 20α-HSO was higher (2.8-, 3.9- and 4.4-fold, respectively; p < 0.001) in normal than in tumor sample. The mean tumor:normal expression ratios for 5αR1 and 5αR2 were about 35–85-fold higher than the tumor:normal expression ratios for the HSOs. Similarly, in the unmatched samples, the tumor:normal ratios for 5αR were significantly higher than the ratios for the HSOs. CONCLUSIONS: The study shows changes in progesterone metabolizing enzyme gene expression in human breast carcinoma. Expression of SRD5A1 (5αR1) and SRD5A2 (5αR2) is elevated, and expression of AKR1C1 (20α-HSO), AKR1C2 (3α-HSO3) and AKR1C3 (3α-HSO2) is reduced in tumorous as compared to normal breast tissue. The changes in progesterone metabolizing enzyme expression levels help to explain the increases in mitogen/metastasis inducing 5αP and decreases in mitogen/metastasis inhibiting 3αHP progesterone metabolites found in breast tumor tissues. Understanding what causes these changes in expression could help in designing protocols to prevent or reverse the changes in progesterone metabolism associated with breast cancer

Identification of pyridine analogs as new predator-derived kairomones.

In the wild, animals have developed survival strategies relying on their senses. The individual ability to identify threatening situations is crucial and leads to increase in the overall fitness of the species. Rodents, for example have developed in their nasal cavities specialized olfactory neurons implicated in the detection of volatile cues encoding for impending danger such as predator scents or alarm pheromones. In particular, the neurons of the Grueneberg ganglion (GG), an olfactory subsystem, are implicated in the detection of danger cues sharing a similar chemical signature, a heterocyclic sulfur- or nitrogen-containing motif. Here we used a "from the wild to the lab" approach to identify new molecules that are involuntarily emitted by predators and that initiate fear-related responses in the recipient animal, the putative prey. We collected urines from carnivores as sources of predator scents and first verified their impact on the blood pressure of the mice. With this approach, the urine of the mountain lion emerged as the most potent source of chemical stress. We then identified in this biological fluid, new volatile cues with characteristic GG-related fingerprints, in particular the methylated pyridine structures, 2,4-lutidine and its analogs. We finally verified their encoded danger quality and demonstrated their ability to mimic the effects of the predator urine on GG neurons, on mice blood pressure and in behavioral experiments. In summary, we were able to identify here, with the use of an integrative approach, new relevant molecules, the pyridine analogs, implicated in interspecies danger communication

Ventilatory frequency as a measure of the response of tammar wallabies (Macropus eugenii) to the odour of potential predators

This study uses changes in ventilatory frequency to quantify the physiological response of an Australian terrestrial herbivore, the tammar wallaby (Macropus eugenii), to olfactory cues suggesting the presence of potential predators. Ventilatory frequency proved to be a quantifiable measure to assess the response of this macropod marsupial to olfactory cues. Ventilatory frequency increased from mean resting levels of 45 ± 5.1 breaths min–1 to 137 ± 11.2 breaths min–1 during the first minute of exposure to all odours. These physiological responses diminished over time, with ventilatory frequency in the first minute after introduction of the scents greater than that during the subsequent four, suggesting that the initial reaction was due to disturbance and was investigative in nature. However, the ratio of ventilatory frequency in the remaining 4 min after introduction of the odours compared with before was greater for fox (3.58 ± 0.918) and cat (2.44 ± 0.272) odours than for snake (2.27 ± 0.370), distilled water (1.81 ± 0.463) and quoll (1.71 ± 0.245) odours, suggesting that fox and cat odour provoked a greater response. However, the wallabies’ response to the odour of these introduced predators and to horse odour (2.40 ± 0.492) did not differ. Our study indicates that a long period of co-history with particular predators is not a prerequisite for detection of potentially threatening species. We do not find any support for the hypothesis that an inability to interpret olfactory cues to detect and respond to potential predation by introduced predators is responsible for the decline of these macropod marsupials