Lighting as a Circadian Rhythm-Entraining and Alertness-Enhancing Stimulus in the Submarine Environment

The human brain can only accommodate a circadian rhythm that closely follows 24 hours. Thus, for a work schedule to meet the brain’s hard-wired requirement, it must employ a 24 hour-based program. However, the 6 hours on, 12 hours off (6/12) submarine watchstanding schedule creates an 18-hour “day” that Submariners must follow. Clearly, the 6/12 schedule categorically fails to meet the brain’s operational design, and no schedule other than one tuned to the brain’s 24 hour rhythm can optimize performance. Providing Submariners with a 24 hour-based watchstanding schedule—combined with effective circadian entrainment techniques using carefully-timed exposure to light—would allow crewmembers to work at the peak of their daily performance cycle and acquire more restorative sleep. In the submarine environment, where access to natural light is absent, electric lighting can play an important role in actively entraining—and closely maintaining—circadian regulation. Another area that is likely to have particular importance in the submarine environment is the potential effect of light to help restore or maintain alertness

The Effects of Red and Blue Lights on Circadian Variations in Cortisol, Alpha Amylase, and Melatonin

The primary purpose of the present study was to expand our understanding of the impact of light exposures on the endocrine and autonomic systems as measured by acute cortisol, alpha amylase, and melatonin responses. We utilized exposures from narrowband long-wavelength (red) and from narrow-band short-wavelength (blue) lights to more precisely understand the role of the suprachiasmatic nuclei (SCN) in these responses. In a within-subjects experimental design, twelve subjects periodically received one-hour corneal exposures of 40 lux from the blue or from the red lights while continuously awake for 27 hours. Results showed-that, as expected, only the blue light reduced nocturnal melatonin. In contrast, both blue and red lights affected cortisol levels and, although less clear, alpha amylase levels as well. The present data bring into question whether the nonvisual pathway mediating nocturnal melatonin suppression is the same as that mediating other responses to light exhibited by the endocrine and the autonomic nervous systems

Does architectural lighting contribute to breast cancer?

OBJECTIVES: There is a growing interest in the role that light plays on nocturnal melatonin production and, perhaps thereby, the incidence of breast cancer in modern societies. The direct causal relationships in this logical chain have not, however, been fully established and the weakest link is an inability to quantitatively specify architectural lighting as a stimulus for the circadian system. The purpose of the present paper is to draw attention to this weakness. DATA SOURCES AND EXTRACTION: We reviewed the literature on the relationship between melatonin, light at night, and cancer risk in humans and tumor growth in animals. More specifically, we focused on the impact of light on nocturnal melatonin suppression in humans and on the applicability of these data to women in real-life situations. Photometric measurement data from the lighted environment of women at work and at home is also reported. DATA SYNTHESIS: The literature review and measurement data demonstrate that more quantitative knowledge is needed about circadian light exposures actually experienced by women and girls in modern societies. CONCLUSION: Without such quantitative knowledge, limited insights can be gained about the causal relationship between melatonin and the etiology of breast cancer from epidemiological studies and from parametric studies using animal models

Circadian light

The present paper reflects a work in progress toward a definition of circadian light, one that should be informed by the thoughtful, century-old evolution of our present definition of light as a stimulus for the human visual system. This work in progress is based upon the functional relationship between optical radiation and its effects on nocturnal melatonin suppression, in large part because the basic data are available in the literature. Discussed here are the fundamental differences between responses by the visual and circadian systems to optical radiation. Brief reviews of photometry, colorimetry, and brightness perception are presented as a foundation for the discussion of circadian light. Finally, circadian light (CLA) and circadian stimulus (CS) calculation procedures based on a published mathematical model of human circadian phototransduction are presented with an example

A new approach to understanding the impact of circadian disruption on human health

Abstract Background Light and dark patterns are the major synchronizer of circadian rhythms to the 24-hour solar day. Disruption of circadian rhythms has been associated with a variety of maladies. Ecological studies of human exposures to light are virtually nonexistent, however, making it difficult to determine if, in fact, light-induced circadian disruption directly affects human health. Methods A newly developed field measurement device recorded circadian light exposures and activity from day-shift and rotating-shift nurses. Circadian disruption defined in terms of behavioral entrainment was quantified for these two groups using phasor analyses of the circular cross-correlations between light exposure and activity. Circadian disruption also was determined for rats subjected to a consistent 12-hour light/12-hour dark pattern (12L:12D) and ones subjected to a "jet-lagged" schedule. Results Day-shift nurses and rats exposed to the consistent light-dark pattern exhibited pronounced similarities in their circular cross-correlation functions and 24-hour phasor representations except for an approximate 12-hour phase difference between species. The phase difference reflects the diurnal versus nocturnal behavior of humans versus rodents. Phase differences within species likely reflect chronotype differences among individuals. Rotating-shift nurses and rats subjected to the "jet-lagged" schedule exhibited significant reductions in phasor magnitudes compared to the day-shift nurses and the 12L:12D rats. The reductions in the 24-hour phasor magnitudes indicate a loss of behavioral entrainment compared to the nurses and the rats with regular light-dark exposure patterns. Conclusion This paper provides a quantitative foundation for systematically studying the impact of light-induced circadian disruption in humans and in animal models. Ecological light and activity data are needed to develop the essential insights into circadian entrainment/disruption actually experienced by modern people. These data can now be obtained and analyzed to reveal the interrelationship between actual light exposures and markers of circadian rhythm such as rest-activity patterns, core body temperature, and melatonin synthesis. Moreover, it should now be possible to bridge ecological studies of circadian disruption in humans to parametric studies of the relationships between circadian disruption and health outcomes using animal models.</p

Preliminary evidence for a change in spectral sensitivity of the circadian system at night

BACKGROUND: It is well established that the absolute sensitivity of the suprachiasmatic nucleus to photic stimulation received through the retino-hypothalamic tract changes throughout the 24-hour day. It is also believed that a combination of classical photoreceptors (rods and cones) and melanopsin-containing retinal ganglion cells participate in circadian phototransduction, with a spectral sensitivity peaking between 440 and 500 nm. It is still unknown, however, whether the spectral sensitivity of the circadian system also changes throughout the solar day. Reported here is a new study that was designed to determine whether the spectral sensitivity of the circadian retinal phototransduction mechanism, measured through melatonin suppression and iris constriction, varies at night. METHODS: Human adult males were exposed to a high-pressure mercury lamp [450 lux (170 μW/cm(2)) at the cornea] and an array of blue light emitting diodes [18 lux (29 μW/cm(2)) at the cornea] during two nighttime experimental sessions. Both melatonin suppression and iris constriction were measured during and after a one-hour light exposure just after midnight and just before dawn. RESULTS: An increase in the percentage of melatonin suppression and an increase in pupil constriction for the mercury source relative to the blue light source at night were found, suggesting a temporal change in the contribution of photoreceptor mechanisms leading to melatonin suppression and, possibly, iris constriction by light in humans. CONCLUSION: The preliminary data presented here suggest a change in the spectral sensitivity of circadian phototransduction mechanisms at two different times of the night. These findings are hypothesized to be the result of a change in the sensitivity of the melanopsin-expressing retinal ganglion cells to light during the night

Clinical Study Short-Wavelength Light Enhances Cortisol Awakening Response in Sleep-Restricted Adolescents

Levels of cortisol, a hormone produced by the adrenal gland, follow a daily, 24-hour rhythm with concentrations reaching a minimum in the evening and a peak near rising time. In addition, cortisol levels exhibit a sharp peak in concentration within the first hour after waking; this is known as the cortisol awakening response (CAR). The present study is a secondary analysis of a larger study investigating the impact of short-wavelength (λ max ≈ 470 nm) light on CAR in adolescents who were sleep restricted. The study ran over the course of three overnight sessions, at least one week apart. The experimental sessions differed in terms of the light exposure scenarios experienced during the evening prior to sleeping in the laboratory and during the morning after waking from a 4.5-hour sleep opportunity. Eighteen adolescents aged 12-17 years were exposed to dim light or to 40 lux (0.401 W/m 2 ) of 470-nm peaking light for 80 minutes after awakening. Saliva samples were collected every 20 minutes to assess CAR. Exposure to short-wavelength light in the morning significantly enhanced CAR compared to dim light. Morning exposure to short-wavelength light may be a simple, yet practical way to better prepare adolescents for an active day

Current attitudes towards the use of perioperative analgesics in cats and dogs by Uruguayan veterinarians

In recent decades, several articles have reported significant progress regarding pain treatment in veterinary medicine. This study aims to analyse the attitudes of veterinarians working in small animal practices in Uruguay towards the use of analgesics during the perioperative period. Veterinarians in charge of clinics performing surgeries were interviewed, including clinics located in the capital city, Montevideo (n=59) and the rest of the country (n=81), based on data obtained from the National Veterinary Census in 2010. Most interviews were conducted in person, and if not possible, they were carried out through video calls. According to gender, 54% of interviewees were women and 46% were men, with 95% of them practising in urban areas. The most used drugs were nonsteroidal anti-inflammatory drugs (NSAIDs), with dipyrone (89%) being the most popular. Amongst opioids, pure agonists presented minimal inclusion in analgesic treatment (13%), with tramadol (93%) being the most used opioid. Drugs belonging to other groups were less mentioned. Thirty-eight per cent of the respondents considered that their training in pain management was inadequate. Veterinarians categorised the intensity of pain caused by several surgical procedures as “severe”, however, they used weak opioids such as tramadol or NSAIDs as a single therapy to treat most cases. The scarce use of analgesic drugs and techniques that provide profound analgesia (such as mu-opioid receptor agonists) by Uruguayan veterinarians reveals the need for open discussion, adjustment of attitudes and continuing education on pain management

Perfil da pecuária leiteira em Rondônia.

Dada a importância econômica e social da pecuária leiteira estadual, buscou-se através da aplicação de 361 questionários se conhecer o perfil econômico, social e produtivo predominante na pecuária leiteira estadual. As informações colhidas possibilitou identificar que a produção de leite é a principal fonte de renda em 56% das propriedades visitadas, 47,9% dos produtores apresentaram uma renda média de três a cinco salários mínimos e, 87,3% dos produtores consultados tinham a família como mão-de-obra

Parasitismo natural por helmintos gastrintestinais em búfalos criados em Presidente Médici, Rondônia, Brasil.

O parasitismo natural por helmintos gastrintestinais foi acompanhado em um rebanho bubalino criado no campo experimental da Embrapa Rondônia, em Presidente Médici, RO, através da pesquisa de ovos destes parasitas em amostras de fezes de búfalas e suas respectivas crias. As amostras de fezes foram colhidas semanalmente, diretamente da ampola retal, de búfalas no terço final da gestação. Após o parto, além das búfalas, foram colhidas amostras de fezes dos bezerros, desde o primeiro dia de vida, duas vezes por semana até o 42º dia, e a partir daí semanalmente, até a 30ª semana. As amostras de fezes foram processadas de acordo com as técnicas de Gordon e Whitlock, modificadas e de flutuação simples, adaptada para as amostras com pequenas quantidades de fezes colhidas dos bezerros. Foram consideradas positivas as amostras que apresentaram pelo menos um ovo de helminto ou oocisto de Emeria spp. Nas amostras de fezes das búfalas foi observada uma prevalência de 3,3% para estrongilídeos e 16,6% para Eimeria spp. Nas mostras dos bezerros foi encontrada uma prevalência de 100% para Toxocara vitulorum e para a Eimeria spp., enquanto que para o Strongyloides papillosus e estrongilídeos foi de 36,6% e 76,6%, respectivamente. A média de semanas em que os bezerros permaneceram infectados foi de 8,1, 10,2, 0,4 e 2,4 semanas para T. vitulorum, Eimeria spp., S. papillosus e estrongilídeos, respectivamente. A partir da 18ª semana de vida dos bezerros não foram mais encontrados ovos de T. vitulorum nas amostras de fezes. Ovos de S. papillosus, estrongilídeos e oocisto de Eimeria spp. foram encontrados nas amostras de fezes dos bezerros a partir da sexta, nona e quarta semana de vida dos animais, respectivamente, permanecendo presentes nos exames coprológicos até a 30ª semana.bitstream/item/46295/1/bpd66-bufalo-1.pd