Fairy wrasses perceive and respond to their deep red fluorescent coloration

Fluorescence enables the display of wavelengths that are absent in the natural environment, offering the potential to generate conspicuous colour contrasts. The marine fairy wrasse Cirrhilabrus solorensis displays prominent fluorescence in the deep red range (650–700 nm). This is remarkable because marine fishes are generally assumed to have poor sensitivity in this part of the visual spectrum. Here, we investigated whether C. solorensis males can perceive the fluorescence featured in this species by testing whether the presence or absence of red fluorescence affects male–male interactions under exclusive blue illumination. Given that males respond aggressively towards mirror-image stimuli, we quantified agonistic behaviour against mirrors covered with filters that did or did not absorb long (i.e. red) wavelengths. Males showed significantly fewer agonistic responses when their fluorescent signal was masked, independent of brightness differences. Our results unequivocally show that C. solorensis can see its deep red fluorescent coloration and that this pattern affects male–male interactions. This is the first study to demonstrate that deep red fluorescent body coloration can be perceived and has behavioural significance in a reef fish.     

The nature of the bond between peptide and carrier molecule determines the immunogenicity of the construct.

The influence of the nature of the bond between a peptide and a (lipidic) carrier molecule on the immunogenicity of that construct was investigated. As types of bonds a thioester-, a disulfide-, an amide- and a thioether bond were investigated. As carrier molecules a peptide, an N-palmitoylated peptide or a C(16)-hydrocarbon chain were used. The biostability of the bond between peptide and carrier molecule is thioether > amide > disulfide > thioester. However, the immunogenic potency of the constructs used was found to be thioester > disulfide > amide > thioether. In conclusion, a construct with a bond between peptide and (lipidic) carrier molecule that is more susceptible to biological degradation is more immunogenic when used in a peptide-based vaccine than a bond that is less susceptible to biological degradation.     

Contributions of basic neurochemistry towards a novel concept of epilepsy

Epilepsy is an ancient disorder which treatment over the centuries has been guided by preconceptions regarding its origin. The major improvements in epilepsy management came following the discovery of the EEG and the development of seizure suppressing agents. These advances in diagnosis and anticonvulsant therapy have further ingrained the conviction that epilepsy is a disease of neurons. Evidence presented here is intended to support a different point of view which suggests that the metabolic modifications in epileptogenic tissue denote subtle alterations in the anatomical and biochemical relationship between neurons and their glial envelopes. As a result the extracellular environment of these cells contain higher than normal levels of glutamic acid. This creates an unnatural functional connectivity between neurons so that they establish abnormal synchronous activity between them and become hyperexcitable due to the depolarizing milieu. To compensate for these biochemical changes it is suggested that some thought might be given to epilepsy management by metabolic manipulation. The measures should be directed specifically towards improving the ability of glia to remove glutamic acid from the extracellular milieu. Two obvious possibilities are to enhance glial glutamine synthesis and to improve the interstitial wash-out of glutamic acid in epileptogenic epicenters. Such a therapy would anticipate to gradually diminish seizure incidence and susceptibility without, however, having a direct action on convulsive episodes per se. The approach must be considered an adjunct to current epilepsy treatment and not a substitute for the use of anticonvulsants.Special Issue Dedicated to Dr. Abel Lajtha.     

Cultivation of the sapropelic ciliate Plagiopyla nasuta Stein and isolation of the endosymbiont Methanobacterium formicicum

The sapropelic ciliate Plagiopyla nasuta was isolated and cultured in monoculture. Optimal conditions for growth were: 15–20°C, pH about 7, and about 2% of oxygen in the headspace. Cultures of P. nasuta produced methane. Epifluorescence microscopy revealed the presence of methanogenic bacteria as endosymbionts. An endosymbiont of the ciliate was isolated and identified as Methanobacterium formicicum. In the ciliate cell these methanogens were found to be closely associated with microbody-like organelles. No mitochondria could be detected.     

The effects of abscisic acid on growth and respiratory characteristics of potato tuber tissue discs

Incubation of potato tuber tissue discs on B5 medium supplemented with 1-naphtyl-acetic acid (NAA) led to callus formation, irrespective of the presence of kinetin; without NAA no callus formation occurred. Incubation in the presence of abscisic acid (ABA) reduced the increases in fresh weight and dry weight both in callus-forming and in non-callus-forming tissue. Mitochondrial respiration was lowered by ABA as well. The induction of the alternative, CN-resistant pathway was inhibited by the presence of ABA, especially in mitochondria from non-callus-forming tissue.The in vivo respiration of the callus-forming tissue was higher than that of the non-callus-forming tissue. Total respiration, cytochrome pathway activity and the capacity of the alternative pathway were all lowered in callus-forming tissue by treatment with ABA. The in vivo activity of the alternative pathway was low in all tissue types, especially after ABA-treatment. The slight stimulation by hydroxamates of the oxygen uptake of callus-forming tissue incubated on medium with NAA and ABA indicates the involvement of a hydroxamate-activated peroxidase in the oxygen uptake of this tissue; this peroxidase seemed not to participate in the oxygen uptake of the other tissues types.In non-callus-forming tissue the oxygen uptake of ABA-treated tissue was very low and almost completely resistant to the combined addition of inhibitors of both the cytochrome and the alternative pathway, indicating that the in vivo activity of the mitochondria in the oxygen uptake of the tissue was very low. The possible causes for this ABA-effect are discussed. In non-callus-forming tissue the treatment with ABA creates a situation which is comparable with that observed in intact potato tubers. This situation is characterized by a tissue respiration lower than that of the isolated mitochondria and an alternative pathway capacity that is low or absent.     

Size-specific mortality patterns in two species of forest floor Collembola

Summary Forest floor populations of Orchesella cincta (L) and Tomocerus minor (Lubbock) (Collembola; Entomobryidae) have been sampled over two generations and from length frequency distributions survivorship curves were constructed for each generation. Size-specific mortality rates were computed from size-specific survivorship data. The results reveal an asymmetrically U-shaped mortality pattern, with disproportionally high juvenile mortality. The pattern changes from one generation to the next, in particular the post-hatching mortality. Evidence from behavioural ecological research on a Collembola-specialized ground beetle is cited in favour of the hypothesis that size-specific mortality patterns are moulded by size-specific predation.     

Reproductive success and clonal genetic structure of the rareArnica montana (Compositae) in The Netherlands

In a medium-sized population ofArnica montana, a threatened species in The Netherlands, the breeding system, reproductive success and genetic clonal structure were studied. Pollination experiments suggested thatA. montana is largely self-incompatible. Inbreeding depression was observed for seedling weight but not for fruit weight and germination rate. Although genetic variation is rather low in this population, the data suggest an outcrossing mating system. Analysis of the genotype of all mapped rosettes in a plot of 100 m² indicated that dense clusters often consist of identical genotypes, suggesting a clonal structure. Open clusters frequently contained several different genotypes. This may be caused by limited fruit dispersal, since seedlings were found mainly within or in the near surroundings of the clusters.     

The Effect of Old Age on the Free-Running Period of Circadian Rhythms in Rat

The free-running period is regarded to be an exclusive feature of the endogenous circadian clock. Changes during aging in the free-running period may therefore reflect age-related changes in the internal organization of this clock. However, the literature on alterations in the free-running period in aging is not unequivocal. In the present study, with various confounding factors kept to a minimum, it was found that the free-running periods for active wakefulness, body temperature, and drinking behavior were significantly shorter (by 12-17 min) in old than in young rats. In addition, it was found that the day-to-day stability of the different sleep states was reduced in old rats, whereas that of the drinking rhythm was enhanced. Transient cycles were not observed, nor were there any age-related differences in daily totals of the various sleep-wake states. The amplitudes of the circadian rhythms of active wakefulness, quiet sleep, and temperature were reduced, whereas those of paradoxical sleep and quiet wakefulness remained unchanged.     

Inhibition of EGF-Induced Signal Transduction by Microgravity Is Independent of EGF Receptor Redistribution in the Plasma Membrane of Human A431 Cells

Epidermal growth factor (EGF)-induced c-fos and c-jun expression is strongly suppressed in microgravity. We investigate here whether this is due to inhibition of processes occurring during the initiation of EGF-induced signal transduction. For this purpose, EGF-induced receptor clustering is used as a marker. The lateral distribution of EGF receptors is directly visualized at an ultrastructural level by the label-fracture method. Quantification of the receptor distributions shows that EGF-induced receptor redistribution is similar under normal and microgravity conditions. This suggests that microgravity influences EGF-induced signal transduction downstream of EGF binding and EGF receptor redistribution, but upstream of early gene expression in human A431 cells.