Japanese quail (Coturnix japonica) audiogram from 16 Hz to 8 kHz.

The purpose of this study was to determine if the Japanese quail, a domesticated, gallinaceous bird, could detect infrasound. Behavioral thresholds were determined for three birds, two males and one female, ranging from 16 Hz to 8 kHz. The animals' hearing range, at a cutoff of 60 dB SPL (re 20 µN/m2), covers 6.88 octaves, ranging from 59.5 Hz to 7 kHz. All animals had the greatest sensitivity to 2 kHz, with an average threshold of 4.4 dB SPL. Although the birds' threshold at 16 Hz was equivalent to that of humans, at no frequency did the birds' sensitivity ever exceed that of humans. Therefore, the Japanese quail does not hear infrasound.

Environmental exposures, stem cells, and cancer.

An estimated 70-90% of all cancers are linked to exposure to environmental risk factors. In parallel, the number of stem cells in a tissue has been shown to be a strong predictor of risk of developing cancer in that tissue. Tumors themselves are characterized by an acquisition of "stem cell" characteristics, and a growing body of evidence points to tumors themselves being sustained and propagated by a stem cell-like population. Here, we review our understanding of the interplay between environmental exposures, stem cell biology, and cancer. We provide an overview of the role of stem cells in development, tissue homeostasis, and wound repair. We discuss the pathways and mechanisms governing stem cell plasticity and regulation of the stem cell state, and describe experimental methods for assessment of stem cells. We then review the current understanding of how environmental exposures impact stem cell function relevant to carcinogenesis and cancer prevention, with a focus on environmental and occupational exposures to chemical, physical, and biological hazards. We also highlight key areas for future research in this area, including defining whether the biological basis for cancer disparities is related to effects of complex exposure mixtures on stem cell biology.

Dietary polyunsaturated fatty acids modulate adipose secretome and is associated with changes in mammary epithelial stem cell self-renewal.

Chronic low-grade adipose inflammation, characterized by aberrant adipokine production and pro-inflammatory macrophage activation/polarization is associated with increased risk of breast cancer. Adipocyte fatty acid composition is influenced by dietary availability and may regulate adipokine secretion and adipose inflammation. After feeding F344 rats for 20 weeks with a Western diet or a fish oil-supplemented diet, we cultured primary rat adipose tissue in a three-dimensional explant culture and collected the conditioned medium. The rat adipose tissue secretome was assayed using the Proteome Profiler Cytokine XL Array, and adipose tissue macrophage polarization (M1/M2 ratio) was assessed using the iNOS/ARG1 ratio. We then assessed the adipokine's effects upon stem cell self-renewal using primary human mammospheres from normal breast mammoplasty tissue. Adipose from rats fed the fish oil diet had an ω-3:ω-6 fatty acid ratio of 0.28 compared to 0.04 in Western diet rats. The adipokine profile from the fish oil-fed rats was shifted toward adipokines associated with reduced inflammation compared to the rats fed the Western diet. The M1/M2 macrophage ratio decreased by 50% in adipose of fish oil-fed rats compared to that from rats fed the Western diet. Conditioned media from rats fed the high ω-6 Western diet increased stem cell self-renewal by 62%±9% (X¯%±SD) above baseline compared to only an 11%±11% increase with the fish oil rat adipose. Modulating the adipokine secretome with dietary interventions therefore may alter stromal-epithelial signaling that plays a role in controlling mammary stem cell self-renewal.

The Behavioral Effects of Oral Psychostimulant Ingestion on a Laboratory Rat Sample: An Undergraduate Research Experience.

Presented is a lab exercise designed to augment an upper-level undergraduate class covering the topics of psychopharmacology, biopsychology, physiological psychology, or introductory neuroscience. The exercise was developed as a tool to allow students to investigate behavioral correlates of oral psychomotor stimulant ingestion and observe firsthand the benefits and challenges of using animal models to study behavior. The purpose of the exercise was to observe the unconditioned, natural behaviors of laboratory rats prior to, and following, the oral administration of commonly used, over-the-counter psychomotor stimulants, and for students to experience the process of neuroscience research. Of specific interest was the comparison of behaviors demonstrated by the animals following ingestion of the nonprescription stimulants caffeine and pseudoephedrine. Students went through the steps of a research project by actively participating in all aspects of experimental design, including construction of testing apparatus, animal care, drug measurement and dosage, data collection, and analyzing behavioral data to determine animal response to psychomotor stimulant exposure. Through repetition of treatment conditions separated by a clearance phase, students observed experiment replication and learned about a research design commonly applied in animal research. Successful replication of treatment effects also served to exemplify the concepts of reliability and validity in behavioral research, while observable responses in animal models provided students with the opportunity to extrapolate important considerations for differential behavioral effects of psychostimulant consumption in humans.

Audiogram of the mallard duck (Anas platyrhynchos) from 16 Hz to 9 kHz.

The pure-tone thresholds of three mallard ducks were determined from 16 Hz to 9 kHz. The purpose was to determine whether the mallard duck hears infrasound, which then may potentially be used for navigation, similar to how it is proposed that pigeons use it for homing. At a level of 60 dB sound pressure level (re 20 µN/m2), their hearing range extends 6.85 octaves from 66 Hz to 7.6 kHz, with a best sensitivity of 12.5 dB at 2 kHz. However, at no frequency, including the lowest tested, were the ducks' thresholds lower than those of humans. Therefore, unlike pigeons and chickens, but like budgerigars, mallard ducks do not hear infrasound. Thus, the fact that a bird may fly long distances does not necessarily indicate that it hears infrasound.

Audiogram of the chicken (Gallus gallus domesticus) from 2 Hz to 9 kHz.

The pure-tone thresholds of four domestic female chickens were determined from 2 Hz to 9 kHz using the method of conditioned suppression/avoidance. At a level of 60 dB sound pressure level (re 20 µN/m(2)), their hearing range extends from 9.1 Hz to 7.2 kHz, with a best sensitivity of 2.6 dB at 2 kHz. Chickens have better sensitivity than humans for frequencies below 64 Hz; indeed, their sensitivity to infrasound exceeds that of the homing pigeon. However, when threshold testing moved to the lower frequencies, the animals required additional training before their final thresholds were obtained, suggesting that they may perceive frequencies below 64 Hz differently than higher frequencies.

Conditioned suppression/avoidance as a procedure for testing hearing in birds: the domestic pigeon (Columba livia).

Although the domestic pigeon is commonly used in learning experiments, it is a notoriously difficult subject in auditory psychophysical experiments, even those in which it need only respond when it detects a sound. This is because pigeons tend to respond in the absence of sound-that is, they have a high false-positive rate-which makes it difficult to determine a pigeon's audiogram. However, false positives are easily controlled in the method of conditioned suppression/avoidance, in which a pigeon is trained to peck a key to obtain food and to stop pecking whenever it detects a sound that signals impending electric shock. Here, we describe how to determine psychophysical thresholds in pigeons using a method of conditioned suppression in which avoidable shock is delivered through a bead chain wrapped around the base of a pigeon's wings. The resulting audiogram spans the range from 2 to 8000 Hz; it falls approximately in the middle of the distribution of previous pigeon audiograms and supports the finding of Kreithen and Quine (Journal of Comparative Physiology 129:1-4, 1979) that pigeons hear infrasound.