bluuebunny/crossref_metadata_2025 huggingface dataset:
Treatment and disposal of refinery sludges: Indian scenario
Authors: Bhattacharyya J. K. , Shekdar A. V.
Published: April 2009

Crude oil is a major source of energy and feedstock for petrochemicals. Oily sludge, bio-sludge and chemical sludge are the major sludges generated from the processes and effluent treatment plants of the refineries engaged in crude oil refining operations. Refineries in India generate about 28,220 tons of sludge per annum. Various types of pollutants like phenols, heavy metals, etc. are present in the sludges and they are treated as hazardous waste. Oily sludge, which is generated in much higher amount compared to other sludges, contains phenol (90-100 mg/kg), nickel (17-25 mg/kg), chromium (27-80 mg/kg), zinc (7-80 mg/kg), manganese (19-24 mg/kg), cadmium (0.8-2 mg/kg), copper (32-120 mg/kg) and lead (0.001-0.12 mg/kg). Uncontrolled disposal practices of sludges in India cause degradation of environmental and depreciation of aesthetic quality. Environmental impact due to improper sludge management has also been identified. Salient features of various treatment and disposal practices have been discussed. Findings of a case study undertaken by the authors for Numaligarh Refinery in India have been presented. Various system alternatives have been identified for waste management in Numaligarh Refinery. A ranking exercise has been carried out to evaluate the alternatives and select the appropriate one. A detailed design of the selected waste management system has been presented.
Suitability of shredded tyres as a substitute for a landfill leachate collection medium
Authors: Park Jae K. , Edil Tuncer B. , Kim Jae Y. , Huh Mock , Lee Sung Ho , Lee Jung Jun
Published: April 2009

A series of tests were conducted to investigate the fate of heavy metals and gasoline components in a simulated landfill, consisting of a 30 cm thick clay liner and a leachate collection layer containing tyres as well as in two test cells installed in a landfill. Arsenic, selenium, mercury, barium, and lead concentrations were lower while zinc concentration was higher in the tank containing tyre-chips than the tank without tyre-chips. When samples were filtered, however, concentrations of zinc as well as other inorganics were lower in the tank containing tyre-chips, indicating that metals in the leachate exposed to tyre-chips travel more slowly in a subsurface environment due to filtering effect.

In a test cell study, arsenic, cobalt, lead and nickel concentrations were lower in the cell containing tyre-chips than in the cell without tyre-chips, except iron and zinc. Both tests indicate that some inorganic contaminants are sorbed to tyre-chips. Gasoline components were also significantly sorbed by tyre-chips in field cell tests. Although tyre-chips are known to leach organic and inorganic contaminants, concentrations in field conditions will be lower than the reported experimental results since the tests were performed under worst-case scenarios. If tyre-chips are used in areas where contamination levels are high, then they can be used as a sorbent for environmental clean-up.
Genetic algorithms as a promising tool for optimisation of the MSW collection routes
Authors: Viotti Paolo , Polettini Alessandra , Pomi Raffaella , Innocenti Carlo
Published: April 2009

Important advantages, including reductions in fuel consumption and labour cost, arise from the optimal design of solid waste (SW) collection routes. Further, optimal design can reduce vehicle maintenance expenditures and improve traffic conditions in urban areas.

To date, optimal routes have been developed according to intuitive methodologies and field experience. However, increasing attention is being devoted to innovative approaches, such as those able to simulate complex collection systems. To analyse these complexities, operational research applications are used. They are typically based on the implementation of heuristic procedures allowing for high quality solutions to the problem at hand.

From a computational point of view, however, heuristic procedures have a complexity which is o(n3), where n is the number of points which have to be visited during each route. This is a limit for an accurate representation of urban areas and for the quality of the calculated solutions.

An alternative methodology, which is the subject of this paper, is based on a genetic algorithm. Also, an ad hoc algorithm, developed in the framework of a wider research, is illustrated.

Results of a preliminary field test conducted for verification are also presented.
Study on composition and particle characteristics of shredded municipal waste for the improvement of separation efficiency in a municipal bulky waste processing facility
Authors: Sekito Tomoo , Tanaka Nobutoshi , Matsuto Toshihiko
Published: April 2009

In order to propose a new and more efficient method of separation for shredded municipal bulky waste (SBW), particle characteristics (namely shape, density and terminal settling velocity) were investigated. It was found that particles of the combustibles such as wood, paper and plastics were included in the fraction smaller than 50 mm. Consequently, separation of SBW into combustibles and non-combustibles by particle size is difficult. Since the particles of the various materials are of all shapes, it is difficult to sort them by shape discrimination. The overall separation efficiencies using air flow and density for SBW separation were estimated and the maximum values are as high as approximately 90% and 99% respectively. However, because of the overlapping ranges of the terminal settling velocities in air for glass, metals, rubber, and plastics, the overall efficiency will become smaller if those materials are major components of the feed. It is concluded that density separation is more suitable for the separation of combustibles and non-combustibles in SBW than air separation.
Physical and chemical processes in baled waste fuel, with emphasis on gaseous emissions
Authors: Nammari Diauddin R. , Hogland William , Moutavtchi Viatcheslav , Marques Marcia , Nimmermark Sven
Published: April 2009

Over a period of seven months, the temperature and the emissions from six cylindrical and two rectangular stored bales containing waste for later use as fuel were measured. The bales were kept at two different ranges of temperatures: 30-35°C and 20-25°C respectively. It was found that only the rectangular bales showed significant production of CO2. The increase of emission for one of the rectangular bales kept at 30-35°C, was 0.246% vol. CO2 per day for a 2-week period, after which there was a decrease of CO2 concentrations at a rate of 0.0224% vol. during a 32-week period. The other rectangular bale kept at 20-25°C, exhibited a similar trend. However, the increase of CO2 concentrations was less at a rate of 0.0259% vol. per day during a 8-week period, after which the CO2 emission decreased at a rate of 0.0224% vol. per day during a 25-week period. All the bales exhibited aerobic decomposition in the sampling point. However on measuring the leachate concentrations, it was evident that the bales were actually in the equivalent acid-generating phase of a young landfill. The temperature inside the bales did not increase higher than the ambient air temperature.
Intensive aerobic bioconversion of sewage sludge and food waste into fertiliser
Authors: Wang Jing-Yuan , Stabnikova Olena , Ivanov Volodymyr , Tay Stephen Tiong-Lee , Tay Joo-Hwa
Published: April 2009

The aim of this research was to verify the possibility of recovering the nutrients present in sewage sludge and vegetable food waste as fertiliser after aerobic thermophilic intensive bioconversion. The process was performed in a closed reactor under controlled conditions of aeration, stirring and pH, at a temperature of 60°C, after addition of a starter bacterial culture of Bacillus thermoamylovorans SW25. End product with the best fertilising properties was obtained when sewage sludge, mixed with food waste, CaCO3 and an artificial bulking agent was thermally pre-treated. The content of volatile solids and organic carbon decreased from 82.8% to 62.3% and from 37.7% to 32.5% of total solids (TS) respectively, during 12 days of biocon-version. The stable organic fertiliser produced was a powder with moisture content of 5%. Furthermore, 3.4% of nitrogen, 0.4% of phosphorus and 2.9% of potassium were also present. Addition of 10-15g of this fertiliser to 1 kg of poor fertility soil increased the growth of different plants by 113-164%.
Detection of gas leakage from landfills using infrared thermography - applicability and limitations
Authors: Lewis Amanda W. , Yuen Sam T.S. , Smith Alan J.R.
Published: April 2009

Although landfill gas emission can be greatly reduced by extraction and converting gas to energy, in practice not all gas can be collected and some leaks can still occur. Management of landfill gas can be improved if leaks can be detected and rectified effectively. This paper provides a brief review of methods available for detecting landfill leakage, with a focus on infrared thermography. It then describes a study which was conducted to test if an infrared camera can be used to detect gas leaks accurately by identifying them as anomalies. It examined the applicability and limitations of the technique by investigating fundamental factors such as weather conditions, ground conditions and distance of sensor from source. The paper also describes a test case conducted to reinforce the findings. It concluded that unless all the fundamental factors are clearly understood and addressed, the technique currently can only be used as a screening tool rather than as a precise tool to detect landfill gas leakages. For this reason, it would be difficult to use the technique as a basis for modelling gas emission from landfills.
Report: Cost and financing of municipal solid waste collection services in Istanbul
Authors: Doğan Karadağ , Süleyman Sakar
Published: April 2009

The collection is a high priority in the management of solid wastes in a modern city, and in order to plan and operate a collection service well, the cost and financial sources must be known and understood in detail. In this study the cost of collection services and environmental tax are evaluated for the year 2001 in Istanbul. The percentage of the employees working in municipal solid waste collection services is 83% by the private sector and 17% by the public sector. With privatisation, the labour costs can be reduced by approximately 75%. The unit collection cost ranges from 12.2 US$/ton to 50.7 US$/ton, and the average collection cost for Istanbul is 24.4 US$/ton. The cost of the collection service is about 70% of the total solid waste management costs, the cost of transfer is 17% and the regular disposal cost amounts to 13%. The proportion of collected tax to expenditures of waste collection varies from 3% to 67%.

The management of solid wastes accounts for between 12 and 25% of the total expenditure of municipal authorities.
Household food waste to wastewater or to solid waste? That is the question
Authors: Diggelman Carol , Ham Robert K.
Published: April 2009

Decision makers need sound analyses of economic and environmental impacts of options for managing household food waste. Food waste impacts public health (it rots, smells, and attracts rodents) and costs (it drives collection frequency). A life cycle inventory is used to quantify total materials, energy, costs and environmental flows for three municipal solid waste systems (collection followed by compost, waste-to-energy or landfill) and two wastewater systems (kitchen food waste disposer followed by rural on-site or municipal wastewater treatment) for food waste management. Inventory parameters are expressed per 100 kg of food waste (wet weight) to place data on a normalised basis for comparison. System boundaries include acquisition, use and decommissioning. Parameters include inputs (land, materials, water) and output emissions to air, water and land. Parameters are ranked simply from high to low. Ranking highest overall was the rural wastewater system, which has a high amount of food waste and carrier water relative to the total throughput over its design life. Waste-to-energy was second; burning food waste yields little exportable energy and is costly. Next, municipal wastewater tied with landfill. Municipal wastewater is low for land, material, energy and cost, but is highest for food waste by-product (sludge). Landfill ranks low for air emissions and cost. Compost ranks lowest; it has the lowest material and water inputs and generates the least waste-water and waterborne waste.
Life cycle analysis of municipal solid waste management possibilities in Asturias, Spain
Authors: Rodríguez-Iglesias Jesús , Marañón Elena , Castrillón Leonor , Riestra Pablo , Sastre Herminio
Published: April 2009

Directive 1994/62 concerning packaging and packaging waste and Directive 1999/31 related to waste disposal will substantially modify the management and treatment of Municipal Solid Waste (MSW) in Europe. In this study, a life cycle analysis has been carried out of the different possibilities of managing Municipal Solid Waste in Asturias. The “Integrated Waste Management” (IWM-1) model was employed, analysing the different alternatives for collection and treatment of MSW. This model predicts overall environmental burdens of MSW management systems and includes a parallel economical model. The sources of costs in the different systems of collection and treatment of MSW were considered in the economical analysis, as well as the sources of resource gathering that may be obtained via the sale of recovered materials. What emerges from this study is the soundness of management strategies based on biological treatment technologies in comparison with thermal treatments, together with the need to increase the level of collection at source.
Solid waste disposal in urban areas and health - the case of Belo Horizonte, Brazil
Authors: Heller Léo , Catapreta Cícero Antonio Antunes
Published: April 2009

The presence of sanitary or controlled landfill in urban areas and its implications for the health of the population that lives in its bordering area has been little investigated. The presence of these deposits, with design or operational problems, can end up providing a likely location for the proliferation of diverse vectors and favouring uncontrolled emissions, which may affect health, both for the people that work and live in these places and those that live nearby. This paper describes a study carried out in the city of Belo Horizonte, Brazil, with the objective of associating the presence of the BR 040 sanitary landfill, located in the urban environment, and the health of the neighbouring population. There were 475 possibilities of occurrences studied, covering 19 different combinations for association between the exposure factor and the groupings of researched diseases (respiratory diseases, diarrhoea and skin diseases). However, of this total only 33 results were shown to be significant in showing the existence of an association. For these results, the variable exposures identified as a risk factor showed an odds ratio ranging between 1.20 and 13.75. Although without an evidenced relationship, respiratory diseases appeared as a relevant outcome in the study, as they were present in 23 of the 33 studied combinations in which the results were significant.
Report: Management problems of solid waste landfills in Kuwait
Authors: Al-Yaqout Anwar F. , Hamoda Mohamed F.
Published: April 2009

This paper evaluates current operational practices in municipal solid waste landfills in Kuwait to provide existing knowledge on uncontrolled landfilling and associated problems of solid waste disposal in developing countries. The current landfilling practices are safe neither for humans nor for the environment. The landfill sites receive all kinds of wastes such as food wastes, oil products, debris, dead animals, agricultural wastes, chemical wastes, wastewater and sewage sludge. The wastes are dumped, spread and compacted in an uncontrolled manner and cover material is not applied regularly. Dust created within the landfill site and gas emissions cause a public nuisance. The characteristics of leachate formed indicate high organic content and presence of heavy metals, salts and nutrients. There are no provisions for leachate or landfill gas collection at the landfill sites. Recommendations for adjustment in landfill operation have been made in recognition of the transition period that is experienced in proceeding from the past and present to the future management of landfills in Kuwait to safeguard the public health and protect the environment.
Anaerobic thermophilic treatment of cattle manure in UASB reactors
Authors: Castrillón L. , Vázquez I. , Marañón E. , Sastre H.
Published: April 2009

Cattle manure was characterised after filtration through a 1-mm sieve and subsequently treated in a 9-l volume Upflow Anaerobic Sludge Blanket (UASB) reactor made of transparent PVC at a thermophilic temperature (55°C). Different Hydraulic Retention Times (HRT)(22.5, 16, 10.6, 8.9 and 7.3 days) were employed and organic matter, total solids and metals were determined, as was the production of biogas. After screening, the COD of the manure subjected to anaerobic thermophilic treatment varied between values of 33,382 and 45,513 mgO2 l-1. The highest percentage of COD removal obtained was 79.7% for an HRT of 22.5 days and there was a fraction refractory to biodegradation of 11%, calculated using Chen & Hashimoto’s model.

Finally, the results obtained at a thermophilic temperature were compared with those obtained at a mesophilic temperature (obtained in a previous work). The reduction in COD was slightly greater under mesophilic conditions, though the main advantage of thermophilic anaerobic treatment is the faster inactivation of viruses and bacteria.
Changes in the quality of landfill leachates from recent and aged municipal solid waste
Authors: Khattabi Hicham , Aleya Lotfi , Mania Jacky
Published: April 2009

A leachate study was conducted at the Etueffont landfill (Belfort, France), to examine differences in leachate composition between old and new areas of the fill and their seasonal evolution. It was based on hourly (1999), monthly (1998-1999) and annual (1993 to 1998) samplings of domestic landfill leachate. Variations in flow rate, rainfall, temperature, electrical conductivity, O2, pH, Cl, SO4, Zn, Cu, Fe, Ni, HCO3, NO3, NH4, BOD and COD were monitored. The results from monthly samplings showed close coupling between flow and concentrations of all parameters measured in the leachate. Indeed, these latter parameters decreased with increasing flow rates. Also, mass emissions per unit waste mass decreased with increasing waste age. The hourly monitoring pointed out an increase in electrical conductivity, chloride and COD concentrations in the middle of the day. This was most likely attributable to temperature fluctuations.
The Suprachiasmatic Nucleus in Organotypic Slice Cultures of the Common Vole (Microtus arvalis): Comparison of Development with Rat and Hamster and the Effect of Age
Authors: Van der Zee Eddy A. , Jansen Koen , Gerkema Menno P.
Published: April 2009

The intrinsic properties of the suprachiasmatic nucleus (SCN), the site of the main circadian pacemaker in mammals, have recently been studied in vitro by means of organotypic slice culturing. So far, only neonatal rats and mice have been used for such developmental and functional analyses of the isolated pacemaker. Here, the authors present a comparative developmental study of the SCN of voles, rats, and hamsters in organotypic slice cultures. In contrast to strictly circadian organization of behavior in rats and hamsters, common voles ( Microtus arvalis) are characterized by large variability in the strength of circadian organization of behavior. It is not known to what extent this variability is reflected in the intrinsic features of the SCN. Cultures were prepared from rat, hamster, and vole pups (6 to 9 days old) for the purpose of species comparison. In addition, the authors studied the relation between age and development in cultures from pup (7 to 10 days old), juvenile (15 to 16 days old), and young adult (1 to 2 months old) voles. In contrast to the situation in rat and hamster, the most striking feature in neonatal voles is the variability in shape of the final, fully developed culture and its poor resemblance with the in vivo SCN. The SCN of adult voles, however, could be cultured successfully while retaining its morphological organization seen in situ. Phase-contrast microscopy and immunocytochemical staining for vasopressin and glial fibrillary acidic protein revealed that cultures of pup and juvenile voles still have potential for neurogenesis and morphological reorganization. Young voles, therefore, can serve as a model to study the developmental establishment of a functional circadian pacemaker, while adult voles allow the study of intrinsic pacemaker properties in relation to previously recorded behavior of the donor and aging-related pacemaker dysfunction.
Evidence of an Annual Rhythm in a Small Proportion of Siberian Hamsters Exposed to Chronic Short Days
Authors: Anchordoquy Hannah C. , Lynch G. Robert
Published: April 2009

Siberian hamsters are photoperiodic seasonally breeding rodents. To date, there has been no evidence that Siberian hamsters exhibit an annual rhythm in reproductive, thermoregulatory, molt, or body mass changes. However, given that the termination of their winter cycle is under endogenous control, the authors thought it possible that under particular conditions, other aspects of their seasonal cycle may be endogenously mediated. Consequently, the authors monitored the reproductive condition, body mass, and molt of hamsters chronically exposed to short days (LD 9:15) for up to 2 years. All animals were taken from previous experiments and had exhibited gonadal regression, followed by refractoriness to shorts days and spontaneous gonadal growth, as well as a complete cycle of body mass and molt changes. Although some hamsters died during the study, the authors continued to monitor some animals for up to 106 weeks of short-day exposure. Of the 57 animals monitored, 4 (7.02%) exhibited a second cycle of reproductive regression and recrudescence. Furthermore, the timing of the second regression was similar in the 4 animals, occurring about 1 year after the initial short-day exposure (50.5 ± 1.71 weeks). However, the timing of the second bout of recrudescence was more variable, occurring at about week 80 (79.5 ± 8.01 weeks). Hamsters exhibited regressed gonads for about 7 months (29.0 ± 8.02 weeks). Although the body mass of the 4 hamsters declined at the time of the second cycle of gonadal regression, it never recovered. No hamster exhibited a second molt cycle. These observations indicate that a small percentage of Siberian hamsters chronically exposed to short days can exhibit an annual cycle of reproduction.
Differential Control of Morning and Evening Components in the Activity Rhythm of Drosophila melanogaster—Sex-Specific Differences Suggest a Different Quality of Activity
Authors: Helfrich-Förster Charlotte
Published: April 2009

The rhythms of locomotor activity of male and virgin or mated female flies were compared in the Drosophila melanogaster wild-type strains Canton S, Berlin, and Oregon R. Under light-dark conditions, most flies showed a bimodal activity pattern with a morning peak around lights-on and an evening peak before lights-off. For all strains, a distinct sexual dimorphism was observed in the phase of the morning peak. Males had a significantly earlier morning peak than females and consequently a larger phase angle between morning and evening peak ([.Psi]m, e). Under constant dark conditions, the morning component merged with the evening component to a unimodal activity band in about half of the flies. In those flies who maintained bimodality, the sex-specific difference in [.Psi]m, e disappeared. Other sex-specific differences were now apparent: Males showed a shorter free running period than females, and in two of the three strains, females were more active than males. Morning and evening components seem to contribute to the free-running period. Spontaneous or externally provoked change in [.Psi]m, e were correlated with period changes. In some flies, the morning and the evening components showed splitting, indicating that they are the output of two different oscillators. The sexual dimorphism in the phase of the morning peak under LDconditions suggests that the function of activity during morning and evening peak might be different, for example, during the morning peak, males are active to find females. Overall, the results underline the multioscillatory nature of Drosophila's circadian system.
Circadian Rhythm of ERG in Iguana iguana: Role of the Pineal
Authors: Miranda-Anaya Manuel , Bartell Paul A. , Yamazaki Shin , Menaker Michael
Published: April 2009

In green iguanas, the pineal controls the circadian rhythm of body temperature but not the rhythm of locomotor activity. As part of a program to investigate the characteristics of this multioscillator circadian system, the authors studied the circadian rhythms of the electroretinographic response (ERG) and asked whether the pineal gland is necessary for the expression of this rhythm. ERGs from a total of 24 anesthetized juvenile iguanas were recorded under four different conditions: (a) complete darkness (DD), (b) dim light-dark cycles (dLD), (c) constant dim light (dLL), and (d) pinealectomized in DD. Results demonstrate that the b-wave component of the ERG shows a very clear circadian rhythm in DD and that this rhythm persists in dLL and entrains to dLD cycles. The ERG response is maximally sensitive during the subjective day. Pinealectomy does not abolish the circadian rhythm in ERG, demonstrating that the oscillator responsible for the ERG rhythm is located elsewhere.
Fluorescent Differential Display Identifies Circadian Clock-Regulated Genes in Arabidopsis thaliana
Authors: Kreps Joel A. , Muramatsu Takamichi , Furuya Masaki , Kay Steve A.
Published: April 2009

Circadian rhythms in gene expression were first observed in plants more than 13 years ago, but the underlying mechanism controlling rhythmic gene expression is still not understood. The isolation of novel circadian clock-controlled genes (ccgs) is likely to provide new tools for studying circadian rhythms. Fluorescent differential display (FDD) was used to screen Arabidopsis thaliana mRNAs for cycling transcripts. Seventy PCR primer pairs were screened, and 17 different cycling bands were observed out of an estimated 10,500 bands screened. The identities of 10 bands were determined, and the rhythmic gene expression was confirmed using northern blot analysis. The 10 cycling bands represent 7 different genes, 6 of which are present in the databases and 1 that does not match anything in current databases. The rhythmic expression of the 7 genes is composed of four distinct phases of clock regulation. The results demonstrate that FDD can be used to isolate ccgs. The genes identified in this screen range from known A. thaliana ccgs, as well as genes shown to be clock controlled in other plant species, to a novel gene that may encode a pioneer protein. Further study of these ccgs is likely to increase our understanding of circadian-regulated gene expression.
Rhythmic Activity of Uptake Hydrogenase in the Prokaryote Rhodospirillum rubrum
Authors: Van Praag Esther , Degli Agosti Robert , Bachofen Reinhard
Published: April 2009

Growth of Rhodospirillum rubrum was followed in cultures kept under anoxic conditions at constant temperature in either continuous light (LL, 32°C) or continuous darkness (DD, 32°C and 16°C). In DD, only small modifications of the turbidity were detected; linear regression analysis nevertheless gives a very significant slope ( t(34) = 13.07, p <10–14, with R2 of 0.834). Mean generation times reflected these differences of growth with 11.9 ± 0.5 h in LL and 43.2 ± 1.1hinDD at 32°C and 37.4 ± 1.0 h at 16°C cultures. The uptake hydrogenase (Hup) activity has been followed in situ in whole cells of R. rubrum grown in the same conditions, and a clear ultradian rhythm of activity has been observed. Indeed, after about 12 h in the new media, a rapid rise of hydrogenase activity was observed in both LL and DD cultures after which it decreased again to very low values. The activity of Hup continued to show such fluctuations during the rest of the experiment, both in DD and in LL, during the growth and stationary phases. The Lomb-Scargle power periodogram method demonstrates the presence of a clear rhythmic Hup activity both in LL and DD. In the LL-grown cultures, the oscillating activity is faster and continues throughout the growth and the stationary phases, with an ultradian period of 12.1 ± 0.5 h. In DD, the slow-growing bacteria showed an ultradian oscillatory pattern of Hup activity with periods of 15.2 ± 0.5 h at 32°C and 23.4 ± 2.0 h at 16°C. The different periods obtained for LL-and DD-grown bacteria are significantly different.
Circadian Clock Controlling Egg Hatching in the Cricket (Gryllus bimaculatus)
Authors: Itoh Masanori T. , Sumi Yawara
Published: April 2009

Adult crickets ( Gryllus bimaculatus) were maintained under a 12-h light:12-h dark cycle (LD 12:12). After oviposition, their eggs were incubated under different lighting regimens at 23°C, and temporal profiles of egg hatching were examined. When the eggs were incubated in LD 12:12 or in DL 12:12 with a phase difference of 12 h from LD 12:12, throughout embryogenesis, 88% to 97% of hatching occurred within 3 h of the dark-light transition on days 17 and 18 of embryogenesis; the phases of the egg-hatching rhythms in the LD 12:12 and DL 12:12 groups differed by about 12 h. In eggs incubated in constant darkness (DD) throughout embryogenesis, a circadian (about 24 h) rhythm of hatching was found, and the phase of the rhythm was similar to that seen in eggs incubated in LD 12:12, but not DL12:12, throughout embryogenesis. When eggs that had been incubated in DD after oviposition were transferred to DL 12:12 in the middle or later stages of embryogenesis and were returned to DD after three cycles of DL 12:12, the rhythm of hatching synchronized (entrained) to DL 12:12. However, when eggs in the earlier stages of embryogenesis were transferred from DD to DL 12:12 and returned to DD after three cycles, 52% to 94% of hatching did not entrain to DL12:12. To determine whether photoperiodic conditions to which the parents had been exposed influenced the timing of egg hatching, adult crickets were maintained in DL 12:12, and their eggs were incubated in LD 12:12, DL 12:12, or DD throughout embryogenesis. The egg-hatching rhythm was also found in the eggs incubated under these three lighting regimens. In DD, the phase of the rhythm was similar to that seen in eggs incubated in DL12:12, not LD 12:12, throughout embryogenesis. The results indicate that in the cricket, the timing of egg hatching is under circadian control and that the circadian rhythm of hatching entrains to 24-h light:dark cycles, but only if the light:dark cycles are imposed midway through embryogenesis. Therefore, by midembryogenesis, a circadian clock has been formed in the cricket, and this is entrainable to light:dark cycles. In addition, the photoperiodic conditions to which the parents (probably the mothers) have been exposed influence the timing of hatching, suggesting that maternal factors may regulate the timing of egg hatching.
Modeling the Dual Pacemaker System of the tau Mutant Hamster
Authors: Oda Gisele A. , Menaker Michael , Friesen W. Otto
Published: April 2009

Circadian pacemakers in many animals are compound. In rodents, a two-oscillator model of the pacemaker composed of an evening ( E) and a morning ( M) oscillator has been proposed based on the phenomenon of “splitting” and bimodal activity peaks. The authors describe computer simulations of the pacemaker in tau mutant hamsters viewed as a system of mutually coupled Eand M oscillators. These mutant animals exhibit normal type 1 PRCs when released into DD but make a transition to a type 0 PRC when held for many weeks in DD. The two-oscillator model describes particularly well some recent behavioral experiments on these hamsters. The authors sought to determine the relationships between oscillator amplitude, period, PRC, and activity duration through computer simulations. Two complementary approaches proved useful for analyzing weakly coupled oscillator systems. The authors adopted a “distinct oscillators” view when considering the component E and M oscillators and a “system” view when considering the system as a whole. For strongly coupled systems, only the system view is appropriate. The simulations lead the authors to two primary conjectures: (1) the total amplitude of the pacemaker system in taumutant hamsters is less than in the wild-type animals, and (2) the coupling between the unit E and M oscillators is weakened during continuous exposure of hamsters to DD. As coupling strength decreases, activity duration ([.alpha]) increases due to a greater phase difference between E and M. At the same time, the total amplitude of the system decreases, causing an increase in observable PRC amplitudes. Reduced coupling also increases the relative autonomy of the unit oscillators. The relatively autonomous phase shifts of E and M oscillators can account for both immediate compression and expansion of activity bands in tau mutant and wild-type hamsters subjected to light pulses.
Light Pulses Suppress Responsiveness within the Mouse Photic Entrainment Pathway
Authors: Khammanivong Ali , Nelson Dwight E.
Published: April 2009

We have characterized a decrease in photic responsiveness of the mammalian circadian entrainment pathway caused by light stimulation. Phase delays of the running-wheel activity rhythm were used to quantify the photic responsiveness of the circadian system in mice (C57BL/6J). In an initial experiment, the authors measured the responsiveness to single “saturating” light pulses (“white” fluorescent light; [.approxequal]1876 [.mu]W; 15 min). In two additional experiments, the authors measured responses to this stimulus at several time points following a saturating pulse at CT 14 or CT 16. Data from these experiments were analyzed in two manners. Experiment 2 was analyzed assuming that the phase of the circadian pacemaker was unchanged by an initial pulse, and Experiment 3 was analyzed assuming that the initial pulse induced an instantaneous phase delay. Results reveal a significant reduction in responsivity to light that persists for at least 2 h and possibly up to 4 h after the initial stimulus. Immediately after the stimulus, the responsiveness of the photic entrainment pathway was reduced to levels [.lessequal] 12% of normal. After 2 h, the responsiveness was [.lessequal] 42% of normal, and by 4 h, responsiveness had recovered to levels that were [.lessequal] 60% of normal (levels not statistically different from controls). By the following circadian cycle, responsiveness was more completely recovered, although the magnitude of some phase delays remained [.lessequal] 85% of normal. These major reductions in the magnitude of phase delays (and phase response curve amplitude) caused by saturating light pulses confound interpretations of two-pulse experiments designed to measure the rate of circadian phase delays. In addition, the time course for this reduced responsiveness may reflect the time course of cellular and molecular events that underlie light-induced resetting of the mammalian circadian pacemaker.
Effects of Light Intensity and Restraint on Dark Pulse-Induced Circadian Phase Shifting during Subjective Night in Syrian Hamsters
Authors: Dwyer Suzanne M. , Rosenwasser Alan M.
Published: April 2009

Dark pulses presented on a background of constant light (LL) result in phase advances during midsubjective day and early subjective night, and phase delays during late subjective night, as shown in the dark-pulse phase response curve. In hamsters, the phase-shifting effects of dark pulses are thought to be mediated by increased activity, as previous studies have shown that restraining animals during dark pulses blocks the phase shifts observed in midsubjective day and late subjective night. This study focuses on dark-pulse-induced phase shifting during early subjective night, examining the influence of both LL intensity and restraint on the magnitude of these phase shifts. Syrian hamsters were maintained in LL of four different illumination levels (1, 10, 100, or 600 lux) and periodically presented with 6-h pulses (dark pulse alone, restraint alone, or dark pulse plus restraint) beginning at circadian time 11. Phase advances were observed in response to dark pulses alone, and the magnitude of these shifts was dependent on background illumination, with significantly larger advances seen under higher intensities. No relationship was found between the amount of activity displayed during dark pulses and phase shift magnitude. Six-hour periods of restraint resulted in phase delays, the magnitude of which was also dependent on background illumination. Restraining hamsters during dark pulses reduced the magnitude of phase advances, but the extent of this reduction could be predicted from the additive effects of the dark-pulse-alone and restraintalone conditions. These results indicate that the phase-shifting effects of dark pulses during early subjective night are not mediated by behavioral activation and may instead reflect a mirror image of the phase-delaying effects of light pulses at this phase.
Tau Differences between Short-Day Responsive and Short-Day Nonresponsive White-Footed Mice (Peromyscus leucopus) Do Not Affect Reproductive Photoresponsiveness
Authors: Majoy Sean B. , Heideman Paul D.
Published: April 2009

In laboratory-bred rodent populations, intraspecific variation in circadian system organization is a known cause of individual variation in reproductive photoresponsiveness. The authors sought to determine whether circadian system variation accounted for individual variation in reproductive photoresponsiveness in a single, highly genetically variable population of Peromyscus leucopusrecently derived from the wild. Running-wheel activity patterns of male and female mice, aged 70 to 90 days, from artificially selected lines of reproductively photoresponsive (R) and nonresponsive (NR) lines were monitored under short-day photoperiod (8 h light, 16 h dark), long-day photoperiod (16 h light, 8 h dark), and constant darkness (DD). NR mice displayed a significantly longer mean free-running period (24.08 h) in DD compared with R mice (23.75 h), due in large part to a difference between NR and R females (24.25 h vs. 23.74 h, respectively). All other entrainment characteristics (alpha, phase angle of activity) under short days, long days, and DD were similar between R and NR mice. Variation in free- running period and entrainment characteristics has been shown to affect photoresponsiveness in other rodent species by altering the manner in which the circadian system interprets short days. To determine whether variation in photoresponsiveness in P. leucopus is due to differences in free-running period instead of variation downstream from the central circadian clock in the pathway controlling photoresponsiveness, the authors exposed young R and NR mice to DD and measured the effect on reproductive organ development. If variation in free-running period affected how the circadian system of mice interpreted short days, then both R and NR mice exposed to DD should have exhibited a delay in gonadal development. Only R mice exhibited pubertal delay in DD. NR mice exhibited large paired testes, paired seminal vesicles, paired ovaries, and uterine weight typical of mice nonresponsive to short days, whereas R mice exhibited reproductive organ weight typical of mice responsive to short days. These data suggest that despite significant differences in free-running period between R and NR mice, individual variation in photoresponsiveness is not due to differences in how the circadian systems of R and NR mice interpret the LD cycle.
The Timing of the Human Circadian Clock Is Accurately Represented by the Core Body Temperature Rhythm following Phase Shifts to a Three-Cycle Light Stimulus Near the Critical Zone
Authors: Khalsa Sat Bir S. , Jewett Megan E. , Duffy Jeanne F. , Czeisler Charles A.
Published: April 2009

Adouble-stimulus experiment was conducted to evaluate the phase of the underlying circadian clock following light-induced phase shifts of the human circadian system. Circadian phase was assayed by constant routine from the rhythm in core body temperature before and after a three-cycle bright-light stimulus applied near the estimated minimum of the core body temperature rhythm. An identical, consecutive three-cycle light stimulus was then applied, and phase was reassessed. Phase shifts to these consecutive stimuli were no different from those obtained in a previous study following light stimuli applied under steady-state conditions over a range of circadian phases similar to those at which the consecutive stimuli were applied. These data suggest that circadian phase shifts of the core body temperature rhythm in response to a three-cycle stimulus occur within 24 h following the end of the 3-day light stimulus and that this poststimulus temperature rhythm accurately reflects the timing of the underlying circadian clock.
5HT7Receptors in the Rodent Suprachiasmatic Nucleus
Authors: Gannon Robert L.
Published: April 2009

Serotonergic modulation of circadian rhythms in rodent model preparations has received considerable attention over the past decade. Investigators have also been trying to determine which of the many serotonin receptor subtypes may be mediating the effects of serotonin in the suprachiasmatic nucleus, the location of the biological clock that generates the circadian rhythms. Asingle study in 1993 using the in vitro rat hypothalamic slice preparation suggested that serotonergic modulation of circadian rhythms at the level of the suprachiasmatic nucleus was acting via the newly discovered 5HT7receptor subtype. Since that initial claim, serotonin modulation of circadian rhythms at the level of the suprachiasmatic nucleus has generally been attributed to 5HT7receptor activation. However, when trying to cite relevant literature in support of 5HT7involvement, it becomes evident that attributing rhythm-related serotonin activity in the suprachiasmatic nucleus to 5HT7receptors may be somewhat premature. There are issues related to pharmacological specificity, species-specific results, and significant knowledge gaps that necessitate a careful review of the literature to make a judgment as to whether 5HT7receptors are responsible for serotonergic activity in the rodent suprachiasmatic nucleus. In addition, there is sufficient data available at present to make an initial determination as to the degree of 5HT7receptor involvement at any level in the generation or modulation of circadian rhythms in rodent species.
Serotonergic Modulation of Retinal Input to the Mouse Suprachiasmatic Nucleus Mediated by 5-HT1B and 5-HT7 Receptors
Authors: Smith Bret N. , Sollars Patricia J. , Dudek F. Edward , Pickard Gary E.
Published: April 2009

Serotonin (5-HT) and 5-HT receptor agonists can modify the response of the mammalian suprachiasmatic nucleus (SCN) to light. It remains uncertain which 5-HT receptor subtypes mediate these effects. The effects of 5-HT receptor activation on optic nerve–mediated input to SCN neurons were examined using whole-cell patch-clamp recordings in horizontal slices of ventral hypothalamus from the male mouse. The hypothesis that 5-HT reduces the effect of retinohypothalamic tract (RHT) input to the SCN by acting at 5-HT1B receptors was tested first. As previously described in the hamster, a mixed 5-HT1A/1B receptor agonist, 1-[3-(trifluoromethyl)phenyl]-piperazine hydrochloride (TFMPP), reduced the amplitude of glutamatergic excitatory postsynaptic currents (EPSCs) evoked by selectively stimulating the optic nerve of wild-type mice. The agonist was negligibly effective in a 5-HT1B receptor knockout mouse, suggesting minimal contribution of 5-HT1A receptors to the TFMPP-induced reduction in the amplitude of the optic nerve–evoked EPSC. We next tested the hypothesis that 5-HT also reduces RHT input to the SCN via activation of 5-HT7 receptors. The mixed 5-HT1A/7 receptor agonist, R(+)-8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide (8-OH-DPAT), reduced the evoked EPSC amplitude in both wild-type and 5-HT1B receptor knockout mice. This effect of 8-OH-DPAT was minimally attenuated by the selective 5-HT1A receptor antagonist WAY 100635 but was reversibly and significantly reduced in the presence of ritanserin, a mixed 5-HT2/7 receptor antagonist. Taken together with the authors' previous ultrastructural studies of 5-HT1B receptors in the mouse SCN, these results indicate that in the mouse, 5-HT reduces RHT input to the SCN by acting at 5-HT1Breceptors located on RHT terminals. Moreover, activation of 5-HT7 receptors in the mouse SCN, but not 5-HT1A receptors, also results in a reduction in the amplitude of the optic nerve–evoked EPSC. The findings indicate that 5-HT may modulate RHT glutamatergic input to the SCN through 2 or more 5-HT receptors. The likely mechanism of altered RHT glutamatergic input to SCN neurons is an alteration of photic effects on the SCN circadian oscillator.
Influence of Light on Feeding Anticipatory Activity in Goldfish
Authors: Aranda A. , Madrid J. A. , Sánchez-Vázquez F. J.
Published: April 2009

Most animals when presented with food on a periodic basis develop feeding anticipatory activity (FAA). The objective of the present study was to investigate the synchronization of activity rhythms to light and feeding in single goldfish given a single daily meal and exposed to different light regimes. In the 1st experiment, the group of fish fed at the end of the day showed a longer FAA (228 ± 27 min) than the group fed 1 h after lights-on (97 ± 31 min). In the 2nd experiment, goldfish under conflicting zeitgebers, LD (T = 26) and feeding (T = 24) cycles, initially synchronized to the light cycle although feeding time gradually assumed greater importance as the experiment progressed. In the 3rd experiment, after altering the feeding cycles by advancing or delaying feeding time by 4 h in LD 0.25:23.75, most goldfish resynchronized to the feeding stimulus and developed FAA. In conclusion, the authors' results revealed that FAAin goldfish is driven by an endogenous timing system that is entrainable by periodic feeding and influenced by the light regime.
SCN Efferents to Peripheral Tissues: Implications for Biological Rhythms
Authors: Bartness T. J. , Song C. K. , Demas G. E.
Published: April 2009

The suprachiasmatic nucleus (SCN) is the principal generator of circadian rhythms and is part of an entrainment system that synchronizes the animal with its environment. Here, the authors review the possible communication of timing information from the SCN to peripheral tissues involved in regulating fundamental physiological functions as revealed using a viral, transneuronal tract tracer, the pseudorabies virus (PRV). The sympathetic nervous system innervation of the pineal gland and the sympathetic outflow from brain to white adipose tissue were the first demonstrations of SCN-peripheral tissue connections. The inclusion of the SCN as part of these and other circuits was the result of lengthened postviral injection times compared with those used previously. Subsequently, the SCN has been found to be part of the sympathetic outflow from the brain to brown adipose tissue, thyroid gland, kidney, bladder, spleen, adrenal medulla, and perhaps the adrenal cortex. The SCN also is involved in the parasympathetic nervous system innervation of the thyroid, liver, pancreas, and submandibular gland. Individual SCN neurons appear connected to more than one autonomic circuit involving both sympathetic and parasympathetic innervation of a single tissue, or sympathetic innervation of two different peripheral tissues. Collectively, the results of these PRV studies require an expansion of the traditional roles of the SCN to include the autonomic innervation of peripheral tissues and perhaps the modulation of neuroendocrine systems traditionally thought to be controlled solely by hypothalamic stimulating/inhibiting factors.