ILLUMINATION OF UPPER AND MIDDLE VISUAL FIELDS PRODUCES EQUIVALENT SUPPRESSION OF MELATONIN IN OLDER VOLUNTEERS

Bright light treatment has become an important method of treating depression and circadian rhythm sleep disorders. The efficacy of bright light treatment may be dependent upon the position of the light-source, as it determines the relative illumination in each portion of the visual field. This study compared illumination of upper and middle visual fields to determine whether melatonin suppression is different or equivalent. Thirteen older volunteers received three illumination conditions in counterbalanced orders: 1000 lux in the upper visual field, 1000 lux in the middle visual field, or dim diffuse illumination <5 lux. A four-choice reaction time task was performed during tests to ensure eye direction and illumination of the intended portion of the visual field. Illumination in the upper and middle visual fields significantly suppressed melatonin compared to <5 lux (p<0.001). Melatonin suppression was not significantly different with upper or middle field illumination. These results indicate that bright light treatments placed above the eye level might be as effective as those requiring patients to look directly at the light source. Clinical comparative testing would be valuable. In addition, this study demonstrates that significant suppression of melatonin may be achieved through the use of bright light in healthy older volunteers.     

Celebrating Achim Trebst’s 80th birthday

At the invitation of Govindjee, we reprint here the English translation of the letter, in German, that we sent, on behalf of the Senate and the Presidium as well as the members of the German Academy of Sciences Leopoldina, from Halle (Saale), to Professor Dr. Dr. h.c.mult. Achim Trebst on his 80th birthday. The original of this letter written in German will appear in Jahrbuch 2009, Deutsche Akademie der Naturforscher Leopoldina, Halle (Saale), Wissenschaftliche Verlagsgesellschaft mbH Stuttgart.     

SLEEP-WAKE SCHEDULE DISORDER DISABILITY: A LIFELONG UNTREATABLE PATHOLOGY OF THE CIRCADIAN TIME STRUCTURE

Certain sleep-wake schedule disorders (SWSDs) cannot be successfully managed clinically using conventional methods of sleep therapy. We describe two cases of SWSD, the first following head trauma and the second originating during childhood, that had been misdiagnosed by physicians for many years. After conventional treatment for SWSD with light therapy and melatonin failed to bring about substantial improvement, it was determined that they were suffering from an incurable disability. Hence, we propose new medical terminology for such cases—SWSD disability. SWSD disability is an untreatable pathology of the circadian time structure. Patients suffering from SWSD disability should be encouraged to accept the fact that they suffer from a permanent disability, and that their quality of life can only be improved if they are willing to undergo rehabilitation. It is imperative that physicians recognize the medical condition of SWSD disability in their patients and bring it to the notice of the public institutions responsible for vocational and social rehabilitation. (Chronobiology International, 18(6), 1019–1027, 2001)     

Effect of sucrose on the optical properties of dipalmitoylphosphatidylcholine

The gel to liquid crystal phase transition of dipalmitoylphosphatidylcholine (DPPC) has been followed by the change in absorbance at 400 nm; this change is due to the change in lipid light scattering properties during the transition. The effect of sucrose on the change in absorbance during the transition of DPPC has been investigated. It has been shown that the presence of sucrose or glycerol in the multilamellar liposome suspension increases the change in absorbance due to the main transition, decreases the total absorbance, and decreases the change in absorbance due to the pretransition. This effect of sucrose and glycerol is shown to be an optical effect which is correlated with solvent index of refraction.     

Some Critical Remarks on the Suitability of the Concept of the Photosynthetic Unit in Photosynthesis Research and Phytoplankton Ecology

Based on the classical definition of the photosynthetic unit after Emerson and Arnold, new definitions are presented and their consistency subjected to critical reflection. Modern molecular approaches to determine the physiological condition or even the efficiency of the photosynthetic machinery via determination of the magnitude of the photosynthetic unit are discussed against the background of new data on the dynamics of the thylakoid membrane.     

Quorum responses and consensus decision making

Animal groups are said to make consensus decisions when group members come to agree on the same option. Consensus decisions are taxonomically widespread and potentially offer three key benefits: maintenance of group cohesion, enhancement of decision accuracy compared with lone individuals and improvement in decision speed. In the absence of centralized control, arriving at a consensus depends on local interactions in which each individual''s likelihood of choosing an option increases with the number of others already committed to that option. The resulting positive feedback can effectively direct most or all group members to the best available choice. In this paper, we examine the functional form of the individual response to others'' behaviour that lies at the heart of this process. We review recent theoretical and empirical work on consensus decisions, and we develop a simple mathematical model to show the central importance to speedy and accurate decisions of quorum responses, in which an animal''s probability of exhibiting a behaviour is a sharply nonlinear function of the number of other individuals already performing this behaviour. We argue that systems relying on such quorum rules can achieve cohesive choice of the best option while also permitting adaptive tuning of the trade-off between decision speed and accuracy.     

Predator detection and avoidance by lotic mayfly nymphs of different size

We studied antipredatory responses of lotic mayfly (Baetis) nymphs in a factorial experiment with four levels of fish presence: (1) a freely foraging fish (the European minnow,Phoxinus phoxinus), (2) a constrained fish, (3) water from a fish stream, (4) water from a fishless stream. LargeBaetis nymphs drifted mainly during night-time in treatments involving either the chemical or actual presence of fish, whereas no diel periodicity was observed when the water was not conditioned with fish odour. The response was strongest when the fish was uncaged, which suggests that visual or hydrodynamic cues are needed in addition to chemical ones for an accurate assessment of predation risk. Fish presence had no effect on the drift rates of small nymphs. Instead, they increased their refuge use in the presence of a live fish. Chemical cues alone did not have any effect on the refuge use of any of theBaetis size classes. Our results indicate active drift entry by mayfly nymphs. Because predation pressure is spatially and temporally variable, nymphs must sample the environment in order to locate predator-free areas or areas with low predation risk. Drifting should be the most energy-saving way to do this. To avoid the risk from visually feeding fish, large individuals can sample safely (i.e. enter drift) only at night-time, while the small ones can also do this safely during the day. We suggest that, contrary to some earlier assumptions, mayfly drift is not a fixed prey response. Instead,Baetis nymphs are able to assess the prevailing predation pressure, and they adjust their foraging behaviour accordingly.     

Ligand Binding Kinetics of Substance P and Neurokinin A Receptors Stably Expressed in Chinese Hamster Ovary Cells and Evidence for Differential Stimulation of Inositol 1,4,5-Trisphosphate and Cyclic AMP Second Messenger Responses

Stably transfected Chinese hamster ovary cells expressing either the substance P receptor or neurokinin A receptor were constructed, isolated, and characterized. Equilibrium ligand binding studies performed on whole cells demonstrated that cell lines expressing either of these receptors contained a single class of high-affinity binding sites with an apparent KD of 0.16 nM for the substance P receptor and an apparent KD of 2.1 nM for the neurokinin A receptor. The higher affinity of substance P for its receptor was accounted for by both a greater association rate constant and a lesser dissociation rate constant. The time course and extent of ligand-stimulated inositol 1,4,5-trisphosphate mass increases in both cell lines were similar and displayed rapid and transient kinetics. Ligand-stimulated cyclic AMP accumulation was also apparent in the cell lines, although the time course and magnitude of the responses were substantially different, with the neurokinin A receptor mediating a greater and more prolonged response. These studies establish the presence of functional substance P receptors and neurokinin A receptors in the stably transfected cell lines and provide evidence for agonist-dependent differential stimulation of second messenger responses.     

Effect of light and simulated herbivory on growth of endangered northeastern bulrush,shape Scirpus ancistrochaetus Schuyler

The independent and interactive effects of light and simulated herbivory on growth and biomass allocation in the endangered emergent sedge, Scirpus ancistrochaetus Schuyler, were examined in a 15-week common garden experiment. Light level was manipulated through the use of shade cloth to attain shading levels of 0%, 30%, 63% and 90%, while herbivory was simulated by reducing plant height by 50% six weeks into the experiment. Multivariate Analysis of Variance (MANOVA) of final total (shoot + root) plant mass, leaf width and root to shoot ratio (R:S) indicated overall significant effects of both light and the interaction of light and clipping. Means of these variables decreased with decreasing light level. Furthermore, means of these variables were generally higher for clipped plants than unclipped plants in 0% shade, while they tended to be lower in clipped plants in all other levels of shade. Maximum leaf height was also significantly affected by light. Leaf height was similar in all treatments for the first 11 weeks. For the last four weeks of the experiment, however, leaf height was lowest in plants grown in 0% shade, highest in plants grown in 63 and 90% shade, and intermediate in plants grown in 30% shade. Clipped plants tended to be taller than unclipped plants at lower levels of shade, while the opposite was true at higher levels of shade, although effects were marginally significant. Both light and the interactive effect of light and clipping were important determinants of growth of S. ancistrochaetus in this experiment and therefore may be important influences on its distribution within and among pond habitats.     

Redox dependence of the blue-light-induced phosphorylation of a 100-kDa protein on isolated plasma membranes from tips of coleoptiles

A blue-light-induced rapid phosphorylation of a 100-kDa protein localized in plasma membranes of phototropically sensitive tips of maize (Zea mays L.) coleoptiles was studied. Since, under in-vivo conditions or in a crude homogenate of tips, cytosolic ATP is the phosphate donor for the light-induced phosphorylation of this protein, a subsequent in-vitro phosphorylation by [³²P]ATP is prevented. However, in-vitro irradiation of microsomal membranes isolated from non-irradiated tips followed by a 1-min incubation with [³²P]ATP resulted in a strong phosphorylation (labelling) of the 100-kDa plasma-membrane protein. This process was saturated by a 7-s light pulse (200 μmol photons·m^?2·s^?1). In the absence of [³²P]ATP the capacity for in-vitro phosphorylation of the 100-kDa protein after a 30-s light pulse declined slowly within 60 min but could be reconstituted by a new light pulse in the presence of reducing compounds. Moreover, when plasma membranes which had been stored frozen were used, reducing compounds such as NADH, NADPH, ascorbate, glutathione or dithiotreithol enhanced the light-triggered in-vitro phosphorylation. These compounds were unable to elicit or enhance the phosphorylation in the dark. It is suggested that the transfer of (blue-light) excited electrons from the chromophore moiety of the receptor to the target (either the 100-kDa protein or the protein kinase itself) is facilitated when reducing compounds instantly eliminate the positive charge generated at the chromophore. The transferred electrons could finally alter the redox state and-or the conformation of either the 100-kDa protein, rendering it susceptible to the action of a protein kinase, or the protein kinase which would then be capable of phospho-rylating the 100-kDa protein.