Calcium-sensitive cells of the pars intermedia and osmotic balance in the eel

Summary Freshwater eels were adapted to calcium-free sea water (SW) or 1/3 Ca-free SW. Survival was generally poor in Ca-free SW, although three eels were still in good condition after 19–30 days; survival in 1/3 Ca-free SW was excellent. Osmotic disturbances (increase of plasma osmolarity and sodium levels), which initially occur in Ca-free SW, were no longer detectable after 19–30 days, or in eels in 1/3 Ca-free SW after one month. Plasma calcium sharply decreases initially; it is less depressed after 19–30 days and in 1/3 Ca-free SW. Alterations in the mucus production may be involved in the osmotic changes. Under these conditions no clear stimulation of the calcium-sensitive (Ca-s) cells of the pars intermedia was registered, but in Ca-free SW (1/3 or full strength) the inhibitory effect normally observed in SW does not occur. In a hyperosmotic environment, other ion(s), possibly magnesium, may reduce the response of the Ca-s cells to a lack of environmental calcium.     

Serotonin and MSH secretion: Effect of Parachlorophenylalanine on the pituitary cytology of the eel

Summary Parachlorophenylalanine (pCPA), an inhibitor of tryptophan hydroxylase which depletes brain serotonin in higher vertebrates, was injected into freshwater eels. After 4 or 6 injections (200 mg/kg/day) or 10 injections (100 and 140 mg/kg/day), the animals are paler, with a low melanophore index. In the pituitary gland, granules tend to accumulate in the basal part of the MSH cells and in the perinuclear area. Cells appear smaller with a decreased nuclear area (P< 0.001). In the neurohypophysis, the amount of neurosecretory material is often reduced. Conversely, injections of 5-hydroxytryptophan induce a strong darkening, a result similar to that previously reported in some amphibian species and in one lacertilian species. These data substantiate the hypothesis of a stimulatory influence of 5-hydroxytryptamine on MSH release and possibly its synthesis in the eel and other lower vertebrates.     

The structure of Sipunculus nudus erythrocyte chromatin

The structure of the Sipunculus erythrocyte chromatin has been characterized by electron microscopy and nuclease digestion (staphylococcal nuclease and pancreatic nuclease). Contrary to previous results [1], we were able to isolate and characterize a histone H_2B in sipunculid nuclei. Though the histones H_2A and H_2B were markedly different from their vertebrate homologues, the subunit structure of the chromatin is the same. But the length of the repeat unit of DNA in the chromatin, is 177 ± 5 bp for the sipunculid erythrocyte nuclei, close to that reported for the chromatin of some lower eukaryotes.     

European robins (Erithacus rubecula) lack an increase in testosterone during simulated territorial intrusions

The challenge hypothesis (Wingfield et al. in Am Nat 136:829–846, 1990) predicts that circulating testosterone increases when socially monogamous male birds are challenged during breeding. Although the challenge hypothesis has been confirmed in large-scale interspecific comparisons of seasonal hormone profiles, experimental tests of the challenge hypothesis are still uncommon and the results equivocal. We tested one of the predictions of the challenge hypothesis by investigating the behavioural and hormonal response of free-living European robins during simulated territorial intrusions (STIs) in the breeding season. We conducted STIs by placing a stuffed decoy in a territory and playing robin song. After the behaviour of the focal male had been recorded for at least 10 min, it was captured and a blood sample was taken immediately. Controls were caught within 10 min of the first response of the territory owner. Hormone concentrations were measured by radio-immunoassay. Although previous studies have shown that testosterone has an impact on aggression, European robins do not respond to STIs by increasing circulating levels of testosterone.     

Augmented visual feedback of movement performance to enhance walking recovery after stroke: study protocol for a pilot randomised controlled trial

ABSTRACT: BACKGROUND: Increasing evidence suggests that use of augmented visual feedback could be a useful approach to stroke rehabilitation. In current clinical practice, visual feedback of movement performance is often limited to the use of mirrors or video. However, neither approach is optimal since cognitive and self-image issues can distract or distress patients and their movement can be obscured by clothing or limited viewpoints. Three-dimensional motion capture has the potential to provide accurate kinematic data required for objective assessment and feedback in the clinical environment. However, such data are currently presented in numerical or graphical format, which is often impractical in a clinical setting. Our hypothesis is that presenting this kinematic data using bespoke visualisation software, which is tailored for gait rehabilitation after stroke, will provide a means whereby feedback of movement performance can be communicated in a more meaningful way to patients. This will result in increased patient understanding of their rehabilitation and will enable progress to be tracked in a more accessible way. METHODS: The hypothesis will be assessed using an exploratory (phase II) randomised controlled trial. Stroke survivors eligible for this trial will be in the subacute stage of stroke and have impaired walking ability (Functional Ambulation Classification of 1 or more). Participants (n = 45) will be randomised into three groups to compare the use of the visualisation software during overground physical therapy gait training against an intensity-matched and attention-matched placebo group and a usual care control group. The primary outcome measure will be walking speed. Secondary measures will be Functional Ambulation Category, Timed Up and Go, Rivermead Visual Gait Assessment, Stroke Impact Scale-16 and spatiotemporal parameters associated with walking. Additional qualitative measures will be used to assess the participant's experience of the visual feedback provided in the study. DISCUSSION: Results from the trial will explore whether the early provision of visual feedback of biomechanical movement performance during gait rehabilitation demonstrates improved mobility outcomes after stroke and increased patient understanding of their rehabilitation.Trial registrationCurrent Controlled Trials ISRCTN79005974.     

Action de la prolactine chez l'Anguille

Résumé Les modifications histologiques de la thyroïde de l'Anguille traitée avec la prolactine ovine indiquent une forte activation qui paraît liée à une hypersécrétion d'hormone thyréotrope, les cellules adénohypophysaires élaborant cette stimuline étant très actives.L'emploi de l'iode radioactif ¹³¹I permet de préciser que la prolactine provoque une augmentation de la fixation thyroïdienne de l'isotope, et l'histoautoradiographie met en évidence un accroissement marqué de la synthèse des composés organiques iodés. On observe également une chute plus rapide de la radioactivité sérique, le rapport thyroïde/sérum étant beaucoup plus élevé chez les animaux traités que chez les témoins, par contre l'excrétion de l'iode dans le milieu externe est ralentie.Ces diverses données permettent donc d'établir que la prolactine ovine n'agit pas chez l'Anguille comme une substance antithyroïdienne et ne confirment pas l'hypothèse d'une action goitrogène formulée par Etkin et Gona chez divers Amphibiens. Au contraire, ces résultats sont similaires à ceux de Mazzi et ses collaborateurs sur un autre Amphibien, montrant que la prolactine stimule l'activité fonctionnelle de la thyroïde; cette action s'exerce par l'intermédiaire de l'hypophyse et paraît offrir une analogie avec celle d'un TRF, toutefois le mécanisme initial de ce processus reste à élucider.

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Action of prolactin in eelsIV. Thyroidal metabolism

Summary The histological changes described in the thyroid gland of ovinprolactin treated eels indicate a strong stimulation (Figs. 1 and 2) which seems correlated with a hypersecretion of thyrotrophic hormone as the adenohypophyseal cells elaborating this stimulin are highly activated.In prolactin injected eels, the utilization of radioiodine ¹³¹I demonstrates that the thyroidal iodine uptake increases (Fig. 7) and histoautoradiography shows a significant increase in the synthesis of iodinated organic compounds (Figs. 3 to 6). The thyroid/serum ratio has much higher values than in control animals, in correlation with a decrease in serum radioactivity (Fig. 8); the iodine excretion in water is reduced.These various data establish that ovin prolactin has no antithyroid effect in the eel, although the hypothesis of a goitrogenic action has been formulated for some amphibians by Etkin and Gona. On the other hand, these results are similar to those of Mazzi and his school, obtained in another amphibian, which show that prolactin stimulates the thyroidal functional activity. This action seems mediated by the pituitary gland and appears to be somewhat analogous with that of a thyrotropic releasing factor; however, the initial step of this process remains to be investigated.

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Nous remercions très vivement le NIH de Bethesda, Endocrinology Study Section, qui nous a généreusement offert la prolactine ovine utilisée dans ces expériences, Mr. F. Lachiver et Melle F. Boulu pour les mesures de la radioactivité sérique et de la fixation thyroïdienne totale qu'ils ont bien voulu effectuer, et Meile J. Olivereau, du CNRS, pour son assistance technique dans la réalisation de ce travail.