Editorial: Rising stars in avian physiology: 2022

Recognizing the future leaders of Avian Physiology is fundamental to safeguarding tomorrow’s driving force in innovation. This Research Topic is aimed to supporting scientists in the early stages of their careers across a wide range of disciplines by selecting and publishing their research output at the highest quality standards. In some sense, Avian Physiology is an amalgam of several fields and disciplines. This is reflected in the fact that veterinary oversight of animal research often distinguishes birds from poultry, birds that are used in agriculture. On one hand, avian physiologists who study poultry with the important objective of improving the health and profitability of poultry species are frequently called “poultry scientists”. Poultry scientists have their own journals, such as Poultry Science, and their own societies, such as the Poultry Science Association and others. On the other hand, avian physiologists who study basic mechanisms in a variety of avian species, including poultry species, are often called “ornithologists”. Ornithologists, like poultry scientists, have their own journals, such as Auk and Condor, as well as societies such as the International Ornithological Congress. And there are societies, such as the International Society for Avian Endocrinology, and journals, such as this journal, that address scientific issues from the breadth of Avian Physiology. This Research Topic reflects that breadth

The Bird of Time: Cognition and the Avian Biological Clock

Avian behavior and physiology are embedded in time at many levels of biological organization. Biological clock function in birds is critical for sleep/wake cycles, but may also regulate the acquisition of place memory, learning of song from tutors, social integration, and time-compensated navigation. This relationship has two major implications. First, mechanisms of the circadian clock should be linked in some way to the mechanisms of all these behaviors. How is not yet clear, and evidence that the central clock has effects is piecemeal. Second, selection acting on characters that are linked to the circadian clock should influence aspects of the clock mechanism itself. Little evidence exists for this in birds, but there have been few attempts to assess this idea. At its core, the avian circadian clock is a multi-oscillator system comprising the pineal gland, the retinae, and the avian homologs of the suprachiasmatic nuclei, whose mutual interactions ensure coordinated physiological functions, which are in turn synchronized to ambient light cycles (LD) via encephalic, pineal, and retinal photoreceptors. At the molecular level, avian biological clocks comprise a genetic network of positive elements clock and bmal1 whose interactions with the negative elements period 2 (per2), period 3 (per3), and the cryptochromes form an oscillatory feedback loop that circumnavigates the 24 h of the day. We assess the possibilities for dual integration of the clock with time-dependent cognitive processes. Closer examination of the molecular, physiological, and behavioral elements of the circadian system would place birds at a very interesting fulcrum in the neurobiology of time in learning, memory, and navigation

A Low-Intensity, Hybrid Design Between a Traditional and a Course-Based Research Experience Yields Positive Outcomes for Science Undergraduate Freshmen and Shows Potential for Large-Scale Application

Based on positive student outcomes, providing research experiences from early undergraduate years is recommended for science, technology, engineering, and mathematics (STEM) majors. To this end, we designed a novel research experience called the “STEMCats Research Experience” (SRE) for a cohort of 119 second-semester freshmen with diverse college preparatory levels, demographics, and academic majors. The SRE targeted student outcomes of enhancing retention in STEM majors, STEM competency development, and STEM academic performance. It was designed as a hybrid of features from apprenticeship-based traditional undergraduate research experience and course-based undergraduate research experience designs, considering five factors: 1) an authentic research experience, 2) a supportive environment, 3) current and future needs for scale, 4) student characteristics and circumstances, and 5) availability and sustainability of institutional resources. Emerging concepts for facilitating and assessing student success and STEM curriculum effectiveness were integrated into the SRE design and outcomes evaluation. Here, we report the efficient and broadly applicable SRE design and, based on the analysis of institutional data and student perceptions, promising student outcomes from its first iteration. Potential improvements for the SRE design and future research directions are discussed

Fertility, Belief, and Sexuality

The human ovulatory cycle lasts an average of 28 days and is highly variable both within and among women, making ovulation and the fertile window difficult to estimate in humans. Commonly used methods for estimating fertility assume length consistency during various cycle phases, an assumption that often miscategorizes women as fertile when not and vice versa. This experiment analyzes several of the common methods used to estimate fertility, including forwards and backwards-counting methods and actuarial methods, and compares them against hormonal testing to determine the most accurate method for fertility identification. Additionally, we used hormonal ovulation tests combined with daily journaling reports to determine the degree to which fertility affects sexual desire, likely sexual engagement, and general happiness, as well as a woman’s belief that she is fertile. We hypothesize that women will not be able to accurately predict their fertility and will show increased sexual interest and general happiness during the fertile window. We also hypothesize that estimation methods will have different results than those using confirmed fertility, but that the closest estimation will be backward counting methods estimating fertility as the six-day window ending at thirteen days from the start of menses

Toward the Beginning of Time: Circadian Rhythms in Metabolism Precede Rhythms in Clock Gene Expression in Mouse Embryonic Stem Cells

The appearance, progression, and potential role for circadian rhythms during early development have previously focused mainly on the suprachiasmatic nucleus (SCN) and peri- and postnatal expression of canonical clock genes. More recently, gene expression studies in embryonic stem cells have shown that some clock genes are expressed in undifferentiated cells; however rhythmicity was only established when cells are directed toward a neural fate. These studies also concluded that a functional clock is not present in ESCs, based solely on their gene expression. The null hypothesis underlying the present study is that embryonic stem cells become rhythmic in both clock gene expression and glucose utilization only when allowed to spontaneously differentiate. Undifferentiated stem cells (ESCs, n = 6 cultures/timepoint for all experiments) were either maintained in their pluripotent state or released into differentiation (dESCs, n = 6 cultures/timepoint for all experiments). Glucose utilization was assayed through 2-deoxyglucose uptake measurement, and clock gene and glucose transporter expression was assayed every 4 hours for 2 days in ESCs and dESCs by quantitative PCR (qPCR) in the same cell lysates. Undifferentiated stem cells expressed a self-sustained rhythm in glucose uptake that was not coincident with rhythmic expression of clock genes. This physiological rhythm was paralleled by glucose transporter mRNA expression. Upon differentiation, circadian patterns of some but not all clock genes were expressed, and the amplitude of the glucose utilization rhythm was enhanced in dESCs. These data provide the earliest evidence of a functional circadian clock, in addition to further challenging the idea that rhythmic transcription of clock genes are necessary for rhythmic physiological output and suggest a role for a clock-controlled physiology in the earliest stages of development

The Premammillary Nucleus of the Hypothalamus Is Not Necessary for Photoperiodic Timekeeping in Female Turkeys (\u3cem\u3eMeleagris gallopavo\u3c/em\u3e)

In birds, seasonal reproduction is regulated by day length, with long days in the spring activating the hypothalamic-pituitary-gonadal axis and reproductive behaviors. The photoreceptors mediating this process remain unknown, but recently, the premammillary nucleus (PMM) of the hypothalamus has been implicated as the site of photoperiodic signaling in turkeys. We performed electrolytic lesions of the PMM to elucidate its role in the photoactivation and maintenance of egg production in female turkeys. Our results show that ablation of the PMM does not alter the normal lay cycle. No differences were found between lesioned birds and sham controls in the latency to lay following photostimulation, nor in subsequent egg production over a period of 29 weeks. No differences in the incidence of gonadal regression were found, indicating that the PMM is not essential for the termination of breeding. We conclude that any role of the PMM in photoperiodic regulation, if it exists, is redundant with other components of the system

The effects of aging on sleep parameters in a healthy, melatonin-competent mouse model

Background: Sleep disturbances are common maladies associated with human age. Sleep duration is decreased, sleep fragmentation is increased, and the timing of sleep onset and sleep offset is earlier. These disturbances have been associated with several neurodegenerative diseases. Mouse models for human sleep disturbances can be powerful due to the accessibility to neuroscientific and genetic approaches, but these are hampered by the fact that most mouse models employed in sleep research have spontaneous mutations in the biosynthetic pathway(s) regulating the rhythmic production of the pineal hormone melatonin, which has been implicated in human sleep. Purpose and method: The present study employed a non-invasive piezoelectric measure of sleep wake cycles in young, middle-aged and old CBA mice, a strain capable of melatonin biosynthesis, to investigate naturally-occurring changes in sleep and circadian parameters as the result of aging. Results: The results indicate that young mice sleep less than do middle-aged or aged mice, especially during the night, while the timing of activity onset and acrophase is delayed in aged mice compared to younger mice. Conclusion: These data point to an effect of aging on the quality and timing of sleep in these mice but also that there are fundamental differences between control of sleep in humans and in laboratory mice

Time\u27s Arrow Flies Like a Bird: Two Paradoxes for Avian Circadian Biology

Biological timekeeping in birds is a fundamental feature of avian physiology, behavior and ecology. The physiological basis for avian circadian rhythmicity has pointed to a multi-oscillator system of mutually coupled pacemakers in the pineal gland, eyes and hypothalamic suprachiasmatic nuclei (SCN). In passerines, the role of the pineal gland and its hormone melatonin is particularly important. More recent molecular biological studies have pointed to a highly conserved mechanism involving rhythmic transcription and translation of clock genes . However, studies attempting to reconcile the physiological role of pineal melatonin with molecular studies have largely failed. Recent work in our laboratory has suggested that melatonin-sensitive physiological processes are only loosely coupled to transcriptional oscillations. Similarly, although the pineal gland has been shown to be critical for overt circadian behaviors, its role in annual cycles of reproductive function appears to be minimal. Recent work on the seasonal control of birdsong, however, suggests that, although the pineal gland does not directly affect gonadal cycles, it is important for seasonal changes in song. Experimental analyses that address these paradoxes will shed light on the roles the biological clock play in birds and in vertebrates in general

Development of a Course-Based Undergraduate Research Experience to Introduce Drug-Receptor Concepts

Course-based research experiences (CUREs) are currently of high interest due to their potential for engaging undergraduate students in authentic research and maintaining their interest in science, technology, engineering, and mathematics (STEM) majors. As part of a campuswide initiative called STEMCats, which is a living learning program offered to freshman STEM majors at the University of Kentucky funded by a grant from Howard Hughes Medical Institute, we have developed a CURE for freshmen interested in pursuing health care careers. Our course, entitled “Drug–Drug Interactions in Breast Cancer,” utilized a semester-long, in-class authentic research project and instructor-led discussions to engage students in a full spectrum of research activities, ranging from developing hypotheses and experimental design to generating original data, collaboratively interpreting results and presenting a poster at a campus-wide symposium. Student’s feedback indicated a positive impact on scientific understanding and skills, enhanced teamwork and communication skills, as well as high student engagement, motivation, and STEM belonging. STEM belonging is defined as the extent to which a student may view the STEM fields as places where they belong. The results obtained from this pilot study, while preliminary, will be useful for guiding design revisions and generating appropriate objective evaluations of future pharmacological-based CUREs

Circadian genomics of the chick pineal gland in vitro

<p>Abstract</p> <p>Background</p> <p>Chick pinealocytes exhibit all the characteristics of a complete circadian system, comprising photoreceptive inputs, molecular clockworks and an easily measured rhythmic output, melatonin biosynthesis. These properties make the <it>in vitro </it>pineal a particularly useful model for exploring circadian control of gene transcription in a pacemaker tissue, as well as regulation of the transcriptome by primary inputs to the clock (both photic and noradrenergic).</p> <p>Results</p> <p>We used microarray analysis to investigate the expression of approximately 8000 genes within cultured pinealocytes subjected to both LD and DD. We report that a reduced subset of genes was rhythmically expressed <it>in vitro </it>compared to those previously published <it>in vivo</it>, and that gene expression rhythms were lower in amplitude, although the functional distribution of the rhythmic transcriptome was largely similar. We also investigated the effects of 6-hour pulses of light or of norepinephrine on gene expression in free-running cultures during both subjective day and night. As expected, both light and norepinephrine inhibited melatonin production; however, the two treatments differentially enhanced or suppressed specific sets of genes in a fashion that was dependent upon time of day.</p> <p>Conclusion</p> <p>Our combined approach of utilizing a temporal, photic and pharmacological microarray experiment allowed us to identify novel genes linking clock input to clock function within the pineal. We identified approximately 30 rhythmic, light-responsive, NE-insensitive genes with no previously known clock function, which may play a role in circadian regulation of the pineal. These are candidates for future functional genomics experiments to elucidate their potential role in circadian physiology. Further, we hypothesize that the pineal circadian transcriptome is reduced but functionally conserved <it>in vitro</it>, and supports an endogenous role for the pineal in regulating local rhythms in metabolism, immune function, and other conserved pathways.</p