Temporal variations of nucleosides and nucleotides in rabbit milk

Abstract

Nucleotides and nucleosides have a preeminent role in physiological and biochemical processes for newborns, the major source of these during early development is the breast milk. Different biomolecules exhibit daily fluctuations in maternal milk that could transfer temporal information that synchronize newborn circadian system. As a first approach, we characterized the diurnal profile of nucleotides and nucleosides contained in maternal milk of rabbits during the first week of lactation. It is possible that some nucleosides, such as adenosine, play a relevant role in setting up the emerging circadian rhythmicity, whereas uridine and guanosine could participate in the maintenance of rhythmicity.     

Observations of Spawning Behaviour in Salmoninae: Salmo, Oncorhynchus and Salvelinus

Long-term data from underwater video recordings in the wild and semi-natural channels are compared to the current literature to review the reproductive behaviour of fishes in the subfamily Salmoninae. Male alternative strategies and tactics are discussed. Reproductive behaviour in Salmoninae is divided into different phases related to female nest selection, construction, and completion. Still underwater video frames are used to support conclusions drawn on spawning behaviour.     

Association between light exposure at night and insomnia in the general elderly population: The HEIJO-KYO cohort

Chronic circadian misalignment between the internal and environmental rhythms, which is typically related to night-shift work and clock-gene variants, is associated with disruption of suprachiasmatic nucleus function and increased risk of insomnia. Under controlled laboratory conditions, light at night (LAN) suppresses melatonin secretion, delays the internal biological rhythm, and reduces sleepiness. Therefore, LAN exposure may cause circadian misalignment and insomnia, though it remains unclear in real-life situations whether LAN exposure is associated with insomnia. To evaluate an association between LAN exposure and sleep quality in home settings, we conducted a cross-sectional community-based study in 857 elderly individuals (mean age, 72.2 years). We evaluated bedroom light intensity using a light meter and subjectively and objectively measured sleep quality using the Pittsburgh Sleep Quality Index and an actigraph, respectively, along with urinary 6-sulfatoxymelatonin excretion. Compared with the lowest quartile group of LAN intensity, the highest quartile group revealed a significantly higher odds ratio (OR) for subjective insomnia in a multivariate model adjusted for age, gender, body mass index, daytime physical activity, urinary 6-sulfatoxymelatonin excretion, bedtime, rising time, and day length (adjusted OR, 1.61, 95% confidence interval, 1.05–2.45, p?=?0.029). In addition, higher OR for subjective insomnia was significantly associated with the increase in quartiles of LAN intensity (p_trend?=?0.043). Consistently, we observed significant association trends between the increase in quartiles of LAN intensity and poorer actigraphic sleep quality, including decreased sleep efficiency, prolonged sleep-onset latency, increased wake-after-sleep onset, shortened total sleep time, and delayed sleep-mid time in multivariate models adjusted for the covariates mentioned above (all p_trend?<?0.001). In conclusion, we demonstrated that LAN exposure in home settings is significantly associated with both subjectively and objectively measured sleep quality in a community-based elderly population.     

Social forces can impact the circadian clocks of cohabiting hamsters

A number of field and laboratory studies have shown that the social environment influences daily rhythms in numerous species. However, underlying mechanisms, including the circadian system''s role, are not known. Obstacles to this research have been the inability to track and objectively analyse rhythms of individual animals housed together. Here, we employed temperature dataloggers to track individual body temperature rhythms of pairs of cohabiting male Syrian hamsters (Mesocricetus auratus) in constant darkness and applied a continuous wavelet transform to determine the phase of rhythm onset before, during, and after cohabitation. Cohabitation altered the predicted trajectory of rhythm onsets in 34% of individuals, representing 58% of pairs, compared to 12% of hamsters single-housed as ‘virtual pair’ controls. Deviation from the predicted trajectory was by a change in circadian period (τ), which tended to be asymmetric—affecting one individual of the pair in nine of 11 affected pairs—with hints that dominance might play a role. These data implicate a change in the speed of the circadian clock as one mechanism whereby social factors can alter daily rhythms. Miniature dataloggers coupled with wavelet analyses should provide powerful tools for future studies investigating the principles and mechanisms mediating social influences on daily timing.     

Circadian Rhythms of Locomotor Activity in the Nile Tilapia Oreochromis niloticus

Behavioral rhythms of the Nile tilapia were investigated to better characterize its circadian system. To do so, the locomotor activity patterns of both male and female tilapia reared under a 12:12 h light-dark (LD) cycle were studied, as well as in males the existence of endogenous rhythmicity under free-running conditions (DD and 45 min LD pulses). When exposed to an LD cycle, the daily pattern of activity differed between individuals: some fish were diurnal, some nocturnal, and a few displayed an arrhythmic pattern. This variability would be typical of the plastic circadian system of fish. Moreover, reproductive events clearly affected the behavioral rhythms of female tilapia, a mouth-brooder teleost species. Under DD, 50% (6 of 12) of male fish showed circadian rhythms with an average period (τ) of 24.1±0.2 h, whereas under the 45 min LD pulses, 58% (7 of 12) of the fish exhibited free-running activity rhythms with an average τ of 23.9±0.5 h. However, interestingly in this case, activity was always confined to the dark phase. Furthermore, when the LD cycle was reversed, a third of the fish showed gradual resynchronization to the new phase, taking 7–10 days to be completely re-entrained. Taken together, these results suggest the existence of an endogenous circadian oscillator that controls the expression of locomotor activity rhythms in the Nile tilapia, although its anatomical localization remains unknown.     

Low‐coverage whole‐genome sequencing reveals molecular markers for spawning season and sex identification in Gulf of Maine Atlantic cod (Gadus morhua,Linnaeus 1758)

Atlantic cod (Gadus morhua, Linnaeus 1758) in the western Gulf of Maine are managed as a single stock despite several lines of evidence supporting two spawning groups (spring and winter) that overlap spatially, while exhibiting seasonal spawning isolation. Low‐coverage whole‐genome sequencing was used to evaluate the genomic population structure of Atlantic cod spawning groups in the western Gulf of Maine and Georges Bank using 222 individuals collected over multiple years. Results indicated low total genomic differentiation, while also showing strong differentiation between spring and winter‐spawning groups at specific regions of the genome. Guided regularized random forest and ranked F _ST methods were used to select panels of single nucleotide polymorphisms (SNPs) that could reliably distinguish spring and winter‐spawning Atlantic cod (88.5% assignment rate), as well as males and females (95.0% assignment rate) collected in the western Gulf of Maine. These SNP panels represent a valuable tool for fisheries research and management of Atlantic cod in the western Gulf of Maine that will aid investigations of stock production and support accuracy of future assessments.     

Oviposition site selection and embryo mortality in perch

Egg strands of perch Perca fluviatilis around the margins of a lake were associated significantly with submerged vegetation. The proportion of dead embryos was significantly higher in egg strands deposited directly on the lake bottom than those on submerged vegetation.     

Reproductive biology of the unique mudskipper Periophthalmodon septemradiatus living from estuary to upstream of the Hau River

This study provided new knowledge on reproductive traits of the unique mudskipper Periophthalmodon septemradiatus that is also a potential aquarium pet. Fish specimens were obtained by using fishing rods at the muddy flat in tributaries of the Hau River from August 2017 to July 2018. Data analysis of a collection of 1,504 individuals (930 males and 674 females) showed that the sex ratio of this species was significantly different from the ratio 1:1. As mature gonads were found monthly during the study period, it is suggested that P. septemradiatus is an iteroparous species releasing eggs for a year-round cycle. The fish length at first mature (L_m) showed an increase from estuary to upstream areas. Male P. septemradiatus had higher L_m values than that of females. Likely, the batch fecundity increased from estuary region (5,916 ± 312 SEM eggs) towards upstream area (11,451 ± 953 SEM eggs). The fish total length and weight values had strong positive relationships with batch fecundity, as shown by high determination values (r²), suggesting that batch fecundity increased with fish size. This study provided more information on reproductive biology of P. septemradiatus, which can be utilized for fish population conservation and artificial reproductive study.     

Behaviour and fitness of γHCH/dieldrin resistant and susceptible female Anopheles gambiae and An.stephensi mosquitoes in the absence of insecticide

The effects of gamma HCH/dieldrin resistance genes on various fitness components of mosquito larvae and adult females in the absence of insecticide were investigated in backcrossed strains of Anopheles gambiae Giles and An.stephensi Liston. Among larvae, heterozygotes (RS) developed slightly but significantly faster than homozygotes for resistance (RR) or susceptibility (SS). The lifetime fecundity of RR females in population cages was only half to two-thirds that of SS and RS females despite similar longevities; several reasons were identified: RR gravid females were less responsive to oviposition-site stimuli, their spontaneous activity--as measured in an acoustic actograph--was only half that of SS or RS females, and RR females produced fewer eggs per unit bloodmeal. When inseminated females were recorded in LD 12:12, RR were again less active than SS or RS. When the lighting was switched to a regime simulating full-moonlight, the activity pattern of SS and RS changed and they flew for longer periods. In contrast, the activity of RR females was the same in LD 12:12 as in 'moonlight'. In a test simulation of potential predation, RR mosquitoes took to flight least readily. All component tests on adult females therefore point to RR as being the least fit of the three genotypes. The behavioural tests suggest that resistance has raised the response threshold of RR females to diverse stimuli. A possible physiological mechanism underlying RR behaviour is that a change in the cyclodiene receptor on the chloride channels has increased their permeability to chloride ions, causing hyper-inhibition of the nervous system.