Continuous Artificial Light Research Articles

Variations in photoperiods and their impact on yield, photosynthesis and secondary metabolite production in basil microgreens

BackgroundThe effects of different photoperiods on plant phytochemical synthesis can be improved by adjusting the daily light integral. Photoperiod is one of the most important environmental factors that control growth, plant’s internal rhythm and the synthesis of secondary metabolites. Information about the appropriate standard in terms of photoperiod for growing basil microgreens as one of the most important medicinal plants is limited. In this study, the effects of five different photoperiods, 6 (6 h × 3 cycles), 8 (8 h × 2 cycles), 16, 18, and 24 h day− 1 on the yield, photosynthesis and synthesis of secondary metabolites of three cultivars and one genotype of basil microgreens in floating system were evaluated. The purpose of this research was to determine the feasibility of using permanent light in growing basil microgreens and to create the best balance between beneficial secondary metabolites and performance.ResultsThe results showed that the effects of photoperiod and cultivar on all investigated traits and their interaction on photosynthetic pigments, antioxidant capacity, total phenolic compounds, proline content and net photosynthesis rate were significantly different at the 1% level. The highest levels of vitamin C, flavonoids, anthocyanins, yield and antioxidant potential composite index (APCI) were obtained under the 24-h photoperiod. The highest antioxidant capacity was obtained for the Kapoor cultivar, and the highest total phenolic compound and proline contents were measured for the Ablagh genotype under a 24-h photoperiod. The highest yield (4.36 kg m− 2) and APCI (70.44) were obtained for the Ablagh genotype. The highest nitrate content was obtained with a photoperiod of 18 h for the Kapoor cultivar. The highest net photosynthesis rate was related to the Violeto cultivar under a 24-hour photoperiod (7.89 μmol CO2 m− 2 s− 1). Antioxidant capacity and flavonoids had a positive correlation with phenolic compounds and vitamin C. Yield had a positive correlation with antioxidant capacity, flavonoids, vitamin C, APCI, and proline.ConclusionsUnder continuous light conditions, basil microgreens resistance to light stress by increasing the synthesis of secondary metabolites and the increase of these biochemical compounds made basil microgreens increase their performance along with the increase of these health-promoting compounds. The best balance between antioxidant compounds and performance was achieved in continuous red + blue light. Based on these results, the use of continuous artificial LED lighting, due to the increase in plant biochemical with antioxidant properties and yield, can be a suitable strategy for growing basil microgreens in floating systems.

Continuous artificial light potentially disrupts central and peripheral reproductive clocks leading to altered uterine physiology and reduced pregnancy success in albino mice.

The mechanism behind clock coordination in female reproductive disorders is poorly understood despite the known importance of coordinated and synchronized timing of central and clocks in reproductive organs. We investigated the effect of continuous artificial light (LL) on the central and peripheral reproductive clock gene (Bmal1, Clock, Per1, Per2 and Cry1) and its downstream regulators (Hgf, PR-A and HOXA10) during non-pregnancy and pregnancy phases of female mice. Mice (n = 60) in two sets, were maintained under continuous light (LL) and natural day cycle (LD;12L: 12D) for both non-pregnant and pregnant study. Tissues from hypothalamus-containing SCN, ovary, uterus and serum were collected at different zeitgeber time points (ZT; at 4-h intervals across 24-h periods). LL exposure desynchronized the expressions of the clock mRNAs (Bmal1, Clock, Per1, Per2 and Cry1) in SCN, ovary, and uterus along with Hgf mRNA rhythm. LL significantly increased the thickness of endometrial tissues. Furthermore, the pregnant study revealed lower serum progesterone level during peri- and post-implantation under LL along with downregulated expression of progesterone receptor (PR) as well as progesterone dependent uterine Homeobox A-10 (Hoxa10) proteins with lowered pregnancy outcomes. Our result suggests that LL disrupted the circadian coordination between central and clock genes in reproductive tissue leading to interrupted uterine physiology and altered pregnancy in mice. This led us to propose that duration of light exposure at work-places or home for females is very important in prevention of pregnancy anomalies.

Normal feline reproduction: The queen.

Cats are seasonally polyestrous, meaning they exhibit multiple estrous cycles within a season, followed by a period of non-cyclicity. Cats cycle when the day length is long but can be induced to cycle year-round with 14 h of continuous artificial lighting. The feline estrous cycle includes the following stages: proestrus, estrus, interestrus and, if ovulation occurs, diestrus. Cats are induced ovulators and ovulate in response to multiple natural matings. Successful breeding in a cattery requires knowledge of the female's reproductive cycle, behavior and management, and often improper management can be the sole cause of infertility. The aim of this review is to provide readers with an overview of normal anatomy, cyclicity, management and behavior of the queen. It includes a series of questions veterinarians can ask to obtain a baseline knowledge of the management of the specific breeding set-up. The information in this article is based on the author's experience, as well as drawing on historical and current literature, and provides the most up-to-date review as possible.

Continuous artificial light at night exacerbates diisononyl phthalate-induced learning and memory impairment in mice: Toxicological evidence

Previously, we reported that exposure to diisononyl phthalate (DINP) resulted in cognitive deficits and anxiety in mice (https://doi.org/10.1038/srep14676). Artificial light at night (ALAN) is now recognized as being a potential threat to human health. However, toxicological evidence concerning exposure to a combination of ALAN and DINP in vivo is limited. To this end, mice were orally exposed to different concentrations of DINP for 28 consecutive days, and ALAN (intensity 150 lux, every night for 12 h). The results showed that oxidative stress levels increased with increasing DINP exposure concentrations, which triggered apoptosis (Bcl-2 levels decreased, Bax levels increased), resulting in nerve cell damage and a decline in the learning and memory abilities of mice. The combined effects of ALAN and DINP exposure on the learning ability and memory of mice are more serious than for DINP exposure alone. The antioxidant vitamin E was shown to have a certain antagonistic effect on the oxidative damage caused by ALAN and DINP exposure. These results highlight a previously unknown relationship between exposure to ALAN and DINP-induced learning and memory impairment, and provide evidence that ALAN may be exacerbating the effects of DINP.

White-light emitting diodes’ spectrum effect on photosynthesis and nutrient use efficiency in Podocarpus macrophyllus seedlings

Fast urbanization and population increase resulted in the demand for ornamental seedling supply in a high efficiency under the culture of continuous artificial lighting. Light emitting diode (LED) can be considered as the replacement of high-pressure sodium (HPS) lamps by providing lights with specific wavelengths for plant growth at low energy cost. In this study, nutrient use efficiency was detected in Podocarpus macrophyllus seedlings under lighting spectra generated by white light-emitting diodes (LEDs) (red (R)/green (G)/blue (B)=8.4:75:16.6) and high-pressure sodium (HPS) lamps (R/G/B/=4.3:69.3:26.5). Compared to seedlings under the HPS spectrum, those under white LED spectrum had better growth, greater biomass accumulation, higher photosynthesis and gas exchange. In contrast, LED-spectrum treated seedlings had greater nitrogen (N) and phosphorus (P) contents than HPS-spectrum treated ones. The LED spectrum promoted nutrient use index for both N and P in seedlings compared to the HPS spectrum. The LED spectrum induced steady-state uptake of P but resulted in the dilution of N. In conclusion, white LED can be considered to replace the usage of HPS lamps for the culture of tree seedlings due to the spectrum effect on N utilization, P uptake and the use efficiencies of N and P.

Growth and welfare of submerged Atlantic salmon under continuous lighting

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 10:501-510 (2018) - DOI: https://doi.org/10.3354/aei00289 Growth and welfare of submerged Atlantic salmon under continuous lighting M. Sievers1,2,3,*, Ø. Korsøen1, T. Dempster1,2, P. G. Fjelldal1, T. Kristiansen1, O. Folkedal1, F. Oppedal1 1Institute of Marine Research, 5984 Matredal, Norway 2School of BioSciences, The University of Melbourne, Parkville, Victoria 3010, Australia 3Australian Rivers Institute - Coast & Estuaries, School of Environment and Science, Griffith University, Gold Coast, Queensland 4222, Australia *Corresponding author: m.sievers@griffith.edu.au ABSTRACT: Although surface-based cages dominate the marine finfish aquaculture industry, production issues that arise at the surface such as poor environmental conditions and the presence of parasites has spurred interest in submerging cages. However, submerged culture is not without its own issues; for example, the adverse effects on fish buoyancy levels can alter swimming speeds and cause tilted swimming at night time, leading to reduced growth rates and vertebral deformities. The use of continuous artificial lighting is common practice in surface-based salmon farming to inhibit maturation. Its implementation can also increase swimming speeds at night, and, if used in submerged cages, may reduce the incidence of tilted swimming. Here we compared submerged (below 10 m) and surface culture of Atlantic salmon Salmo salar for 42 d under continuous lighting. The use of continuous lightning during submergence of large (3.4 kg) Atlantic salmon increased swimming speeds, reduced tilted swimming, and spinal deformities did not arise. Submerged culture also decreased infestation by attached sea lice stages by 72%, from 4.4 to 1.2 lice per fish. However, specific growth rates of submerged fish were 30% lower than those of surface-reared fish. Developments in engineering and technologies that allow salmon to refill their swim bladders during submergence show promise in eliminating welfare and growth problems. Robust scientific experiments at full commercial scale of cages and operating systems that consider both production and welfare outcomes are critical to the successful development of submerged farming. KEY WORDS: Aquaculture · Lepeophtheirus salmonis · Parasite control · Salmo salar · Sea lice · Mariculture Full text in pdf format PreviousCite this article as: Sievers M, Korsøen Ø, Dempster T, Fjelldal PG, Kristiansen T, Folkedal O, Oppedal F (2018) Growth and welfare of submerged Atlantic salmon under continuous lighting. Aquacult Environ Interact 10:501-510. https://doi.org/10.3354/aei00289 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 10. Online publication date: November 22, 2018 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2018 Inter-Research.

Effects of light source and intensity on sexual maturation, growth and swimming behaviour of Atlantic salmon in sea cages

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 9:193-204 (2017) - DOI: https://doi.org/10.3354/aei00224 Effects of light source and intensity on sexual maturation, growth and swimming behaviour of Atlantic salmon in sea cages Tom Johnny Hansen*, Per Gunnar Fjelldal, Ole Folkedal, Tone Vågseth, Frode Oppedal Institute of Marine Research, 5984 Matredal, Norway *Corresponding author: tomh@imr.no ABSTRACT: We investigated how highly efficient LED light sources may be used in Atlantic salmon cage farming. Specifically, we tested the incidence of sexual maturation and growth patterns in autumn sea-transferred Atlantic salmon Salmo salar L. during their second sea winter given continuous artificial light (LL) (between 13 January and 18 June) of 5 different intensities using LED sources, compared to a single intensity provided by a metal halide (MH) source or a control treatment of natural light (NL). Growth effects were independent of light source, but increased with irradiance. We propose a model wherein sufficiently high irradiance from the artificial light source will give a long day signal throughout late winter and spring, an intermediate irradiation will give a long day signal until it is outcompeted by the seasonal increase in natural light, and an irradiance that is always below the threshold will not be perceived as different from natural light. Sexual maturation in males (6.1% under NL) was evenly arrested at all intensities, and swimming activity at night increased during winter in lit groups. We conclude that LED lamps may replace MH sources at similar intensity. Reducing the light irradiance of the superimposed light reduced the growth-stimulating effect, but all irradiances reduced the incidence of sexual maturation. KEY WORDS: Salmo salar · Photoperiod · Salmonid aquaculture · Cage environment Full text in pdf format PreviousNextCite this article as: Hansen TJ, Fjelldal PG, Folkedal O, Vågseth T, Oppedal F (2017) Effects of light source and intensity on sexual maturation, growth and swimming behaviour of Atlantic salmon in sea cages. Aquacult Environ Interact 9:193-204. https://doi.org/10.3354/aei00224 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 9. Online publication date: June 20, 2017 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2017 Inter-Research.

Fluorescent light induces neurodegeneration in the rodent nigrostriatal system but near infrared LED light does not

We investigated the effects of continuous artificial light exposure on the mouse substantia nigra (SN). A three month exposure of C57Bl/6J mice to white fluorescent light induced a 30% reduction in dopamine (DA) neurons in SN compared to controls, accompanied by a decrease of DA and its metabolites in the striatum. After six months of exposure, neurodegeneration progressed slightly, but the level of DA returned to the basal level, while the metabolites increased with respect to the control. Three month exposure to near infrared LED light (∼710nm) did not alter DA neurons in SN, nor did it decrease DA and its metabolites in the striatum. Furthermore mesencephalic cell viability, as tested by [3H]DA uptake, did not change. Finally, we observed that 710nm LED light, locally conveyed in the rat SN, could modulate the firing activity of extracellular-recorded DA neurons. These data suggest that light can be detrimental or beneficial to DA neurons in SN, depending on the source and wavelength.

Production of verbascoside and phenolic acids in biomass of Verbena officinalis L. (vervain) cultured under different in vitro conditions

Methanolic extracts from the biomass of Verbena officinalis cultured under continuous artificial light and in darkness on 12 variants of the Murashige and Skoog medium containing different concentrations (0.5–3.0 mg/L) of plant growth regulators: 6-benzyladenine, kinetin, 1-naphthaleneacetic acid and indole-3-butyric acid, were analysed for the amounts of verbascoside and phenolic acids, before and after acid hydrolysis, using the HPLC-DAD method. The amounts of verbascoside were very high (max. 2454.12 mg/100 g DW – light, and 2135.59 mg/100 g DW – darkness). The total amounts of phenolic acids reached a maximum of 46.02 mg/100 g DW (free phenolic acids) and 141.05 mg/100 g DW (bound compounds). The main metabolites were: ferulic, o-coumaric and caffeic acids. The maximum amount of verbascoside was 3.28 times higher than in extracts from the herb of the parent plant. The cultures could be proposed as a potential biotechnological source for selected biologically active compounds.

Phosphorus removal using a microalgal biofilm in a new biofilm photobioreactor for tertiary wastewater treatment

Eutrophication of surface water has been an important environmental issue for nearly half a century. High concentrations of phosphorus contribute to the process of eutrophication, resulting in the demand for effective and economic methods of phosphorus removal from treated water. The aim of this study was to evaluate the capacity for phosphorus removal of a microalgal biofilm during different light regimes. The photobioreactor was operated for nine months each year over a two-year period without interruption and without any need of re-inoculation. The algal biofilm was able to remove 97 ± 1% of total phosphorus from wastewater during 24 h of continuous artificial illumination. The average TP uptake rate in our experiments was 0.16 ± 0.008 g m−2 d−1. Phosphorus removal values ranged from 36 to 41% when the algal biofilm was illuminated by natural light (12 h sunlight–12 h night). The biomass production rate was 12.21 ± 10 g dry weight m−2 d−1 in experiments with continuous artificial light and 5.6 ± 1 g dry weight (DW) m−2 d−1 in experiments with natural light. These results indicate the great potential of microalgal biofilms in the tertiary treatment of wastewater.

The effect of harvesting on biomass production and nutrient removal in phototrophic biofilm reactors for effluent polishing

An increasing number of wastewater treatment plants require post-treatment to remove residual nitrogen and phosphorus. This study investigated various harvesting regimes that would achieve consistent low effluent concentrations of nitrogen and phosphorus in a phototrophic biofilm reactor. Experiments were performed in a vertical biofilm reactor under continuous artificial lighting and employing artificial wastewater. Under similar conditions, experiments were performed in near-horizontal flow lanes with biofilms of variable thickness. It was possible to maintain low nitrogen and phosphorus concentrations in the effluent of the vertical biofilm reactor by regularly harvesting half of the biofilm. The average areal biomass production rate achieved a 7 g dry weight m−2 day−1 for all different harvesting frequencies tested (every 2, 4, or 7 days), corresponding to the different biofilm thicknesses. Apparently, the biomass productivity is similar for a wide range of biofilm thicknesses. The biofilm could not be maintained for more than 2 weeks as, after this period, it spontaneously detached from the carrier material. Contrary to the expectations, the biomass production doubled when the biofilm thickness was increased from 130 μm to 2 mm. This increased production was explained by the lower density and looser structure of the 2 mm biofilm. It was concluded that, concerning biomass production and labor requirement, the optimum harvesting frequency is once per week.

Testing in situ avoidance reaction of vendace, Coregonus albula, in relation to continuous artificial light from stationary vertical split‐beam echosounding

Abstract The in situ avoidance reaction of vendace, Coregonus albula L., in relation to continuous artificial light in terms of a scaring device was tested by split‐beam echosounding. The tests were carried out in the mesotrophic Bigge Reservoir (Germany) in November 2007 and 2008 using a Simrad EK 60 echosounder (120 kHz). An underwater lamp with light turned on and off was lowered to 30 m water depth at four sampling sites. No reaction of vendace was observed for the sampled references (light off), but strong avoidance behaviour by swimming mainly downwards was observed when the light was turned on. The light avoidance reaction was confirmed by the volume backscattering strength (Sv) and calculated fish densities (fish ha−1). The mean fish densities for the samples carried out with light turned on were lower (268 fish ha−1, ±409 SD, n = 32) than for the references with light turned off (5028 fish ha−1, ±2317 SD, n = 56). The related median values (33 and 3726 fish ha−1, respectively, n = 88) differed significantly (Mann–Whitney test, P = <0.001). In conclusion, artificial light has great potential to scare pelagic vendace from areas near the bottom outlets of reservoirs to prevent entrainment losses.

Effects of different long-day photoperiods on somatic growth and gonadal development in Nile tilapia ( Oreochromis niloticus L.)

Long-day photoperiods are considered as an effective managerial tool in manipulating somatic growth and reproduction in a number of fish species. Effects of three different artificial long-day photoperiods on somatic growth and gonadal development of Nile tilapia ( Oreochromis niloticus L.) were investigated in this study. Swim-up fry with a mean initial weight of 0.06 g were exposed to 24L:0D, 20L:4D and 18L:6D artificial photoperiods and ambient light regime (control) for 24 weeks at 27.0 ± 1 °C. The effect of photoperiodic manipulation was only detectable and statistically meaningful during fingerling stage. Long-day photoperiods resulted in significantly higher mean final weights and specific growth rates (SGR) than natural light regime. The highest mean final weight (24.94 ± 0.45 g) and SGR (3.46 ± 0.03% day − 1 ) were obtained under 24L:0D photoperiod. Mean female gonadosomatic index (GSI) and mean oocyte size were significantly lower in fish maintained under continuous light regime (24L:0D) than those of 20L:4D, 18L:6D treatments and control. The highest gonadosomatic indices were recorded in control female and males. Mean oocyte diameter in fish exposed to continuous light was measured as 1.05 ± 0.06 mm with the bulk of the oocytes (60.0%) in pre-vitellogenic stage (≤ 1.20 mm). On the contrary, oocyte size and size distribution of oocytes in 20L:4D, 18L:6D photoperiod groups and control were indicating a more advanced oocyte development stage, i.e. vitellogenic (1.2–1.8 mm) and post-vitellogenic stages (> 2.1–2.4 mm). Basically, results obtained support the idea that continuous artificial lighting may be influential on enhancing somatic growth and delaying gonadal development in Nile tilapia during fingerling stage.

Photostability Determination of Commercially Available Nifedipine Oral Dosage Forms in Iran

Nifedipine (NIF) a 1, 4-dihydropyridine calcium channel antagonist, undergoes photodegradation to nitroso analogues of dehydronifedipine (NDNIF) when exposed to sunlight. Photodegradation products of NIF have no clinical activity, so different formulations of NIF must remain unchanged. If NIF preparations become unstable in exposure to light, they could cause therapeutic failure. The present study was carried out in order to investigate the photostability of commercially available NIF products, in Iran. Three oral NIF formulations available in Iran were studied using indirect sunlight (daylight) and continuous artificial light exposure extending over a period of 12 weeks. The extent of photodecomposition of NIF was determined using a specific reversed phase high performance liquid chromatography (HPLC) method. NIF photodegradation was measured using both pure NIF powder as well as a methanolic NIF solution to determine differences in the effectiveness of artificial light and natural indirect sunlight sources used in this study. All the tested NIF formulations were likely to be photostable up to at least 12 weeks of continuous artificial and natural day light exposure, compared with pure NIF powder and methanolic solution. Photodegradation of NIF powder and methanolic solution exposed to indirect sunlight was faster than the artificial light.

Effects of continuous light and short-day photoperiod on smolting, seawater survival and growth in Atlantic salmon ( Salmo salar)

Duplicate groups of 1-year-old Atlantic salmon were exposed to 5–7 weeks of short days (LD 8.15:15.45) with artificial light, followed by a period of continuous light (LL) for 3 months (A), 2 months (B) or 1 month (C) before transfer to sea cages. Duplicate groups were also exposed to a 2-week period of LD 8.15:15.45, followed by a period of continuous light for 2 months (D). Comparisons were made with fish that were reared under natural light conditions from October onwards (F) and continuous light (E) only. Fish from all groups were transferred to sea cages on 9 June and their survival and growth were monitored until 31 October. There was a significant ( P < 0.001) interaction between light regime and time for all smolt characters measured. Development of smolt colouration, decrease in condition factor, increases in gill Na-K-ATPase activity and the ability to regulate plasma Na + after 24 h in full-strength sea water, indicated that the fish in groups A, B and C completed smoltification 6–8 weeks after the end of the short-day periods. No decrease in the condition factor was recorded for fish in groups D and E. The mortality was 40% for group A and 34% for group B, and 15% or less for the other groups. Groups A and B had probably lost some of the smolt characters by the time of seawater transfer. The specific growth rate in sea water was 1.5% for group F and for the survivors of groups A and B, 1.4% for group C and 1.2% for groups D and E. In conclusion, a short-day regime of 5–7 weeks, followed by continuous artificial light, caused smolt-related changes similar to those found in outdoor-reared fish, whereas this was not so for fish exposed to either a short-day period of only 2 weeks or to continuous artificial light.

Light deprivation increases plasma levels of melatonin during the first 72 h of life in human infants.

The development of rhythmic melatonin secretion in full-term neonates seems to occur at about 12 weeks of age, but activity of the pineal gland from 1 to 12 weeks of age is not well documented. To determine whether the pineal gland actively secretes melatonin and reacts to photoperiodic information during this period, we analyzed 45 full-term infants exposed to continuous artificial light during 24, 48 and 72 h after birth for treatment of hyperbilirubinemia. During this light treatment, the eyes of the neonates were completely covered to avoid damage, thus the infants were under continuous light deprivation. Phototherapy significantly decreased plasma bilirubin during treatment. With regard to pineal gland activity, the shortest period of light deprivation tested, 24 h, significantly increased plasma melatonin levels from 152.66 +/- 11.57 to 244.86 +/- 19.49 ng/l (mean +/- SEM; p < 0.001). The other periods tested, 48 and 72 h of light deprivation, led to similar percentages of melatonin stimulation. These results suggest that the pineal gland of neonates, before displaying rhythmic metabolic activity, is sensitive to changes in environmental illumination, indicating maturity of some features of suprachiasmatic nuclei function.

Melatonin can induce year-round ovarian cyclicity in red deer (Cervus elaphus).

From 17 February 1987 (Day 1) to 5 June 1988 (Day 475), 6 red deer hinds which had been in natural daylength (NL/M) and 6 hinds which had been in continuous artificial light for the previous month (CL/M) were each given melatonin (5 mg in feed) daily at 15:00 h. Six controls (C) received unsupplemented feed. From Day 1 all hinds were in natural daylight and ovarian cyclicity was assessed from plasma progesterone concentrations. Group C first went into anoestrus on 15 March 1987 (Day 27 +/- 9.2 (s.e.m], recommenced cyclicity on 23 October (Day 249 +/- 2.3) and went into anoestrus again on 2 April 1988 (Day 411 +/- 8.7). Group CL/M first went into anoestrus 31 days earlier (P less than 0.05) on 12 February (Day -4 +/- 7.8), before the start of melatonin treatment; 4 hinds then recommenced ovarian cycles 132 days earlier (P less than 0.001) on 13 June (Day 117 +/- 5.8) and continued to cycle for a longer period than did controls. Group NL/M hinds were cyclic at the start of melatonin feeding and continued to cycle for 1 year or more (N = 6). Plasma prolactin concentrations remained suppressed (less than 20 ng/ml) for the duration of melatonin-feeding (Groups CL/M and NL/M) whereas control values (Group C) were elevated (20-120 ng/ml) between April and August (P less than 0.05). The ovarian response by hinds to melatonin therefore depends on initial reproductive status and recent photoperiodic history, and continued administration to cyclic hinds stimulates prolonged ovarian cyclicity irrespective of the time of year.

CONTROLS, ACTH β -ENDORPHIN: DIURNAL RHYTHEMS OF INFANTS IN A NEONATAL INTENSIVE CARE UNIT

To determine whether a diurnal rhythm exists in neonates admitted to neonatal intensive care units (NICU) where there is continuous artificial lighting and periodic nursing and medical care exists, Plasma cortisol, ACTH and β-endorphin (BED) concentrations were measured in two groups of infants and another group of adult human volunteers. As expected, a diurnal rhythm is seen in adults. Plasma concentrations found during morning and (afternoon) hours were: cortisol - 475.0 ± 204.2 (255.0 ± 75.2) nmoles /L; ACTH - 10.9 ± 3.4 (13.0 ± 4.6) pg/mL; β-ED -22.l ± 9.5 (16.8 ± 7.2) pg/mL. A diurnal rhythm was also observed for ACTH and cortisol in neonates (3-4 days postnatally) :cortisol - 340 ± 194.5 (228.8 ± 101.0) nmoles/L; ACTH - 6.3 ± 4.2 (8.8 ± 5.5)pg/mL. Although there was not a statistically significant difference between morning and afternoon β -ED levels in this group, the afternoon levels like the adults were lower: 24.2 ± 13.0 (19 ± 9.8) pg/mL. There was no significant difference between the concentrations of any of the three substances in infants who were severely stressed clinically: cortisol - 320 ± 230.6 (406.4 ± 227.4) nmoles/L; ACTH - 7.0 ± 3.1 (8.0 ± 4.7) pg/mL; β- ED -37.1 ± 19.4 (45.6 ± 35.7) pg/mL. It would appear that a diurnal rhythm exists in neonates within the first few days of postnatal life and that the continuous lighting, medical and nursing interventions do not seem to interfere with this rhythm. Severe stress seems to override this rhythm.

Dark-Period Induction of Zygospores in Mucor

This study was conducted to test the hypothesis that the factor responsible for erratic mating behavior among certain Mucor species is a requirement for an induction period of darkness. Zygospores are formed with continuous natural or artificial light after a dark period. When strains are mated near one another (10 mm apart) and far apart (70 mm) in the same plates, zygospores typically form in the close matings but rarely in the far matings even though the colonies grow together. At 25 C and 20 C the dark effect is pronounced except for M. lusitanicus; at 32 C the effect is less. When 81/2 h of light and 151/2 h of darkness were alternated, some zygospores were produced from da 2 onward, but the numbers, even at da 5, were greatly reduced. Zygospores of the homothallic M. genevensis were formed in both light and darkness but more developed in the dark. When various isolates from ragi were contrasted with appropriate mating types and exposed to daylight and darkness no zygospores were usually formed in the light, but in darkness all but one strain produced numerous zygospores. Different wavelengths of light had little effect on zygospore formation.

Time-restricted feeding of pigs: social and feeding behavior (1984)

Twenty finishing pigs were used to evaluate effects of time-restricted feeding on social interactions and feeding patterns of pigs at feeding time. Correlation analysis for pairs of traits, involving feeding activities, social interactions, and rate of gain indicate that more aggressive pigs went first to the feeder, fed more frequently, and gained faster. Although on continuous artificial lighting, timed-fed pigs displayed more feeding and aggressive behavior during day light hours.; Swine Day, Manhattan, KS, November 15, 1984