https://www.sussex.ac.uk/lifesci/insectnavigation/documents/collettchittkacollett-currbiolreview2013.pdf

Spatial memory in insect navigation.

The pineal gland is a unique organ that synthesizes melatonin as the signaling molecule of natural photoperiodic environment and as a potent neuronal protective antioxidant. An intact and functional pineal gland is necessary for preserving optimal human health. Unfortunately, this gland has the highest calcification rate among all organs and tissues of the human body. Pineal calcification jeopardizes melatonin’s synthetic capacity and is associated with a variety of neuronal diseases. In the current review, we summarized the potential mechanisms of how this process may occur under pathological conditions or during aging. We hypothesized that pineal calcification is an active process and resembles in some respects of bone formation. The mesenchymal stem cells and melatonin participate in this process. Finally, we suggest that preservation of pineal health can be achieved by retarding its premature calcification or even rejuvenating the calcified gland.

Pineal Calcification, Melatonin Production, Aging, Associated Health Consequences and Rejuvenation of the Pineal Gland.

History and recent progress on chytridiomycosis in amphibians

Cell movement is highly sensitive to stimuli from the extracellular matrix and media. Receptors on the plasma membrane in cells can activate signal transduction pathways that change the mechanical behavior of a cell by reorganizing motion-related organelles. Cancer cells change their migration mechanisms in response to different environments more robustly than noncancer cells. Therefore, therapeutic approaches to immobilize cancer cells via inhibition of the related signal transduction pathways rely on a better understanding of cell migration mechanisms. In recent years, engineers have been working with biologists to apply microfluidics technology to study cell migration. As opposed to conventional cultures on dishes, microfluidics deals with the manipulation of fluids that are geometrically constrained to a submillimeter scale. Such small scales offer a number of advantages including cost effectiveness, low consumption of reagents, high sensitivity, high spatiotemporal resolution, and laminar flow. Therefore, microfluidics has a potential as a new platform to study cell migration. In this review, we summarized recent progress on the application of microfluidics in cancer and other cell migration researches. These studies have enhanced our understanding of cell migration and cancer invasion as well as their responses to subtle variations in their microenvironment. We hope that this review will serve as an interdisciplinary guidance for both biologists and engineers as they further develop the microfluidic toolbox toward applications in cancer research.

Microfluidics-based devices: New tools for studying cancer and cancer stem cell migration.

Insects have been extraordinarily successful in occupying terrestrial habitats, in contrast to their mostly aquatic sister group, the crustaceans. This success is typically attributed to adult traits such as flight, whereas little attention has been paid to adaptation of the egg. An evolutionary novelty of insect eggs is the serosa, an extraembryonic membrane that enfolds the embryo and secretes a cuticle. To experimentally test the protective function of the serosa, we exploit an exceptional possibility to eliminate this membrane by zerknullt1 RNAi in the beetle Tribolium castaneum. We analyse hatching rates of eggs under a range of humidities and find dramatically decreasing hatching rates with decreasing humidities for serosa-less eggs, but not for control eggs. Furthermore, we show serosal expression of Tc-chitin-synthase1 and demonstrate that its knock-down leads to absence of the serosal cuticle and a reduction in hatching rates at low humidities. These developmental genetic techniques in combination with ecological testing provide experimental evidence for a crucial role of the serosa in desiccation resistance. We propose that the origin of this extraembryonic membrane facilitated the spectacular radiation of insects on land, as did the origin of the amniote egg in the terrestrial invasion of vertebrates.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2013.1082

The extraembryonic serosa protects the insect egg against desiccation

Most species of birds exhibit well-defined seasonality in their various physiological and behavioral functions like reproduction, molt, bill color etc. such that they occur at the most appropriate time of the year. Day length has been shown to be a major source of temporal information regulating seasonal reproduction and associated events in a number of avian species. The present study aims to investigate the role of photoperiod in control of seasonal cycles in the subtropical male tree sparrow (Passer montanus) and to compare its responses at Shillong (Latitude 25°34'N, Longitude 91°53'E) with those exhibited by its conspecifics and related species at other latitudes. Initial experiment involving study of seasonal cycles revealed that the wild tree sparrows posses definite seasonal cycles of testicular volume, molt and bill color. These cycles were found remarkably linked to annual solar cycle suggesting the possibility of their photoperiodic control. To confirm this possibility in the next experiment, the photosensitive birds were exposed to three different light-dark regimes that were close to what they experience at this latitude: 9L/15D (close to shortest day length), 12L/12D (equinox day length) and 14L/10D (close to longest day length) for 18 months. Tree sparrows showed testicular growth followed by regression and development of photorefractoriness, molting and bill color changes only under long daily photoperiods (12 L and 14 L) but not under short daily photoperiod (9 L). Birds, under stimulatory photoperiods, did not show reinitiation of the above responses after the completion of initiation regression cycle even after their exposure to these photoperiods for 18 months. This precludes the possibility of circannual rhythm generation and suggests the involvement of photoperiodic mechanism in control of their seasonal cycles. Further, replacement of body and primary feathers progressed with gonadal regression only under long days suggesting that the two high energy demanding events of reproduction and molt are phased at two different times in the annual cycle of the bird and are photoperiodically regulated. Results of the final experiment involving exposure of photosensitive birds to a variety of photoperiodic treatments (9L/15D, 10L/14D, 11L/13D, 12L/12D, 14L/10D and 16L/8D) for 30 days suggested that the light falling for 11 h or more is important in inducing testicular growth and function in this species. These results clearly indicate that despite of small photofluctuation, subtropical tree sparrows are capable of fine discrimination of photoperiodic information and use day length as a proximate environmental factor to time their seasonal responses similar to their conspecifics and related species at other latitudes suggesting the conservation of photoperiodic control mechanism in them.

/pdf/photoperiod-as-a-proximate-factor-in-control-of-seasonality-54l9r5zx58.pdf

Photoperiod as a proximate factor in control of seasonality in the subtropical male Tree Sparrow, Passer montanus

Seasonal reproductive cycles of most birds are regulated by photoperiod via neuroendocrine control. Gonadotropin-inhibitory hormone (GnIH) in the hypothalamus has been reported to act as neuroendocrine integrator of photoperiodic cues. In this study, both captive and field investigations were carried out to understand the effects of photoperiod and seasonality on GnIH expression in subtropical tree sparrows. Monthly observations of GnIH mRNA and peptide expression in wild birds over a year revealed a significant increase in GnIH mRNA level and number of GnIH-ir neurons during the non-breeding season when compared with their expression in the breeding season. GnIH-ir neurons were found primarily in the paraventricular nucleus (PVN) with their fibers projecting into the median eminence and some other areas of the brain. In an 8 month-long experiment, birds exposed to short days had higher GnIH expression compared with birds exposed to long days regardless of sampling month. Long-day birds with regressed testes had similar GnIH levels to short-day birds. Though the number of GnIH peptide-expressing neurons ran almost parallel to the levels of GnIH mRNA, they were inversely related to gonadal size in both sexes under natural and artificial photoperiodic conditions. These results clearly indicate an inhibitory role of GnIH in photoperiodic regulation of seasonal reproduction in the tree sparrow.

/pdf/role-of-gnih-in-photoperiodic-regulation-of-seasonal-452c8xtyqj.pdf

Role of GnIH in photoperiodic regulation of seasonal reproduction in the Eurasian tree sparrow.

We investigated seasonal variations in response to photoperiods in subtropical tree sparrow (Passer montanus), by examining the effects of long and short days on stimulation of response and termination of refractoriness, respectively. We also assessed whether photoperiodic effects were sex dependent. In one study, wild sparrows were transferred in each month of the year to artificial long days (14L/10D) for 12 weeks. Birds transferred from November to March (female) or April (male) showed gradual increase in gonadal growth and darkening of bill color, while those transferred from April (female) or May (male) to July underwent gradual regression in the above responses. Moult in the wing primaries and body feathers progressed with gonadal regression and the birds transferred from April/May to October exhibited gradual increase and decrease in feathers moult. In another study, 6 weeks of short day (9L/15D) exposure could recover responsivity to long days in refractory birds. Male and female birds responded almost in similar fashion with some variations. Overall, our results show a gradual change over seasons in responsiveness of the endogenous response system to stimulatory effects of long day length. They suggest roles of both long and short day lengths in regulation of seasonal cycles in subtropical tree sparrows.

Seasonal Variation in Sensitivity of the Photoperiodic Response System in the Subtropical Tree Sparrow (Passer montanus)

Photoperiodic control of testicular growth, histomorphology and serum testosterone levels in the male Eurasian tree sparrow: Involvement of circadian rhythm

We studied the effects of temperature on the photoperiodic regulation of seasonal reproduction and related events in the subtropical tree sparrow at Shillong, India. In the first experiment, one group of birds was maintained in an outdoor open aviary receiving natural photoperiod and temperature conditions, while the other group was exposed to natural photoperiod and constant temperature of 17 ± 2 °C in an outdoor closed aviary for 12 months. Although both sexes achieved peak gonadal growth at the same time (May) under the two conditions, gonadal regression and feathers molt were delayed under the temperature controlled condition. In the second experiment, the groups of birds were exposed to three different temperatures (17, 25 and 30 °C) under both long (LD-14L:10D) and short (SD-9L:15D) day lengths for 7 months. Birds showed relatively small but significant gonadal growth, darkening of bill color and feathers molt only at 30 °C under SD. However, they behaved as though they were under natural conditions and exhibited the above responses significantly at all temperatures under LD. There was delayed gonadal regression at the lower temperature (17 °C), while feathers molt delayed with increasing temperature (25, 30 °C) under LD. These results clearly indicate that temperature modulates photoperiodic seasonal responses in the tree sparrow.

Namram S. Singh

Papers

Photoperiod as a proximate factor in control of seasonality in the subtropical male Tree Sparrow, Passer montanus

Role of GnIH in photoperiodic regulation of seasonal reproduction in the Eurasian tree sparrow.

Seasonal Variation in Sensitivity of the Photoperiodic Response System in the Subtropical Tree Sparrow (Passer montanus)

Photoperiodic control of testicular growth, histomorphology and serum testosterone levels in the male Eurasian tree sparrow: Involvement of circadian rhythm

Temperature modulates photoperiodic seasonal responses in the subtropical tree sparrow, Passer montanus