Untersuchungen Über die Bildung der peritrophischen Membran bei den Insekten

Ohne Zusammenfassung     

Incorporating microglia-like cells in human induced pluripotent stem cell-derived retinal organoids

Microglia are the primary resident immune cells in the retina. They regulate neuronal survival and synaptic pruning making them essential for normal development. Following injury, they mediate adaptive responses and under pathological conditions they can trigger neurodegeneration exacerbating the effect of a disease. Retinal organoids derived from human induced pluripotent stem cells (hiPSCs) are increasingly being used for a range of applications, including disease modelling, development of new therapies and in the study of retinogenesis. Despite many similarities to the retinas developed in vivo, they lack some key physiological features, including immune cells. We engineered an hiPSC co-culture system containing retinal organoids and microglia-like (iMG) cells and tested their retinal invasion capacity and function. We incorporated iMG into retinal organoids at 13 weeks and tested their effect on function and development at 15 and 22 weeks of differentiation. Our key findings showed that iMG cells were able to respond to endotoxin challenge in monocultures and when co-cultured with the organoids. We show that retinal organoids developed normally and retained their ability to generate spiking activity in response to light. Thus, this new co-culture immunocompetent in vitro retinal model provides a platform with greater relevance to the in vivo human retina.     

Thermodynamic functions of biopolymer hydration. I. Their determination by vapor pressure studies,discussed in an analysis of the primary hydration process

The primary hydration process of native biopolymers is analyzed in a brief review of the literature, pertaining to various aspects of biopolymer–water systems. Based on this analysis, a hydration model is proposed that implies that the solution conformation of native biopolymers is stable at and above a critical degree of hydration (h_p′ = 0.06–0.1 g H₂O/g polymer). This water content corresponds to the fraction of strongly bound water, and amounts to ～20% of the primary hydration sphere. In order to test this model, detailed sorption–desorption scanning experiments were performed on a globular protein (α-chymotrypsin). The results obtained are consistent with the proposed hydration model. They show that under certain experimental conditions, sorption isotherms can be obtained that do not exhibit hysteresis. These data represent equilibrium conditions and are thus accessible to thermodynamic treatment. Valid thermodynamic functions, pertinent to the interaction of water with biopolymers in their solution state, can be obtained from these sorption experiments.     

Ecological stress and linear enamel hypoplasia in Cebus

Although it is assumed that monkeys in some environments experience more nutritional or physiological stress than others, little research has been conducted on this topic. This study examines the relationship between linear enamel hypoplasia (LEH) frequency, a physiological indicator of stress, and environmental stressors. To test this relationship, LEH frequencies were calculated for 144 Cebus from 54 locations in Brazil. Habitat, temperature range, and annual rainfall were compared between individuals with and without LEH. The LEH frequency for Cebus from semideciduous forests was significantly higher than that for monkeys from coastal areas, the rainforest, and the savanna (χ² = 9.97, df = 1; P = 0.0016). A significantly higher LEH frequency was also found for monkeys living in environments with the mean annual temperature between 15 and 18°C than for those in environments greater than 18°C (χ² = 7.74, df = 1, P = 0.0054). However, no significant difference was found between LEH frequency and annual rainfall (t = 1.22, P = 0.23) or the average difference in rainfall between the driest and wettest months (t = 0.77, P = 0.44). These results indicate that levels of physiological stress can differ among environments and that habitat and temperature, but not precipitation, may be driving the difference in stress levels among environments. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Responses of MSH and prolactin cells to 5-hydroxytryptophan (5-HTP) in amphibians and teleosts

Summary Injection of 5-hydroxytryptophan (5-HTP), a precursor of serotonin, induces dispersion of melanin in the amphibians, Pleurodeles waltlii (Urodela) and Xenopus laevis (Anura), in the goldfish, Carassius auratus, and in the carp, Cyprinus carpio. It is accompanied by a dispersion of erythrophore pigments. In the pituitaries of Pleurodeles and goldfish, a stimulation of MSH cells, characterized by a significant nuclear hypertrophy, is also observed; in Carassius, MSH cells may become degranulated. Serotonin appears to exert a stimulating effect on MSH release in lower vertebrates. Swimming behavior is disturbed in the goldfish and the carp; gaseous metabolism in the swim-bladder may be affected by injection of 5-HTP, as previously reported in the eel. Prolactin (PRL) cells appear activated, but remain granulated in the treated goldfish. No clear response of PRL cells to injection of 5-HTP can be observed in Pleurodeles. A possible role of serotonin in Pleurodeles submitted to an experimental aeroionization is briefly discussed.     

Response to and transport of brood by workers of Tapinoma erraticum (Formicidae; Dolichoderinae) during nest disturbance

An attempt was made to describe the principle signals involved in the recognition of nymphs by Tapinoma workers. A behavioural measure, the way and extent to which workers transported different objects presented to them, was used to quantify this relationship. These objects were homo- or heterospecific nymphs, or different baits. Two types of test were generally used in such studies: retrieval — bringing back objects to the nest, and removal – transport of objects during displacement of the nest. The second type of test was used in this study. The results, in decreasing order of recognition were as follows. Tapinoma workers transport homospecific and Tetramorium nymphs at 100%. The smaller nymphs of Solenopsis impregnated with Tapinoma extract were transported at 77%. The nymphs of Solenopsis with their own odour were transported at 21%, paper impregnated. with Tapinoma extract at 12%, while ‘odourless’ Tapinoma nymphs and neutral paper were not transported at all. These results imply an intervention of both physical and chemical factors, the threshold significance of signals and their global implication depending on the test situation and its disturbing effect. They also depend on the nature of the different objects presented in combination; Tapinoma workers transport heterospecific brood much less readily in the presence of their own brood. The attractiveness of nymphs is not an all or none phenomenon. In a study of the adoption of homospecific nymphs from another nest, this gradation was apparent in the distribution of nymphs in the nest and their order of transport during removal tests; certain nymphs were left aside in the first 3 days of presentation, were amongst the last to be transported during removal, and then by the most active workers.The perception of the brood by the workers may thus occur at different levels: (1) Perception of a factor that may be vaguely defined as ‘transportable object’ in a removal test — with objects of type ‘nymph’ for example; (2) perception of the species; (3) perception of the colony. The worker ant during its life acquires a certain ‘knowledge’ of its own brood through familiarization, which expresses itself in terms of specific patterns of care for the brood, but this attention, although given preferentially to the brood, is not exclusive under stress.     

Action de la prolactine chez l'Anguille intacte et hypophysectomisée

Résumé Le transfert graduel d'eau douce en eau de mer de l'Anguille argentée n'entraîne pas de variations très significatives de Na⁺ et K⁺ plasmatiques étudiés aux 10, 20, 30 et 50e jours; la calcémie s'abaisse régulièrement alors que la chlorémie s'accroît. L'hypophysectomie, réalisée 24 h avant le transfert, ne modifie pas les réponses trouvées chez l'Anguille intacte en fonction de la durée du séjour en eau de mer. La prolactine ovine injectée chez l'Anguille intacte (10 j) ou hypophysectomisée (20, 30 et 50 j) induit une augmentation très significative des électrolytes étudiés. Ces résultats sont comparés à ceux concernant l'activité de la Na⁺-K⁺-ATPase branchiale, intestinale et rénale. Si une corrélation entre cette activité enzymatique et la différence entre Na⁺ externe et Na⁺ plasmatique est évidente lors de l'augmentation de la salinité, elle n'est plus apparente après hypophysectomie et/ou traitement avec la prolactine en eau de mer.

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Action of prolactin in intact and hypophysectomized eelsVIII. Effects on plasma electrolytes in sea water

Summary Male silver eels were gradually transferred from fresh water to sea water. Plasma Na⁺ and K⁺ levels are not significantly affected after 10, 20, 30 and 50 days, plasma Ca⁺⁺ slowly decreases and plasma Cl^– increases. Similar electrolyte changes occur in eels hypophysectomized the day before their transfer. Ovine prolactin injected immediately after pituitary ablation induces a marked increase of plasma electrolytes in intact (10 daily injections) or hypophysectomized eels injected for 20, 30 and 50 days. These data were compared with those previously obtained on Na⁺-K⁺-ATPase activity in gill filaments, intestinal mucosa and kidney. If there is a positive correlation between gill Na⁺-K⁺-ATPase activity and the difference between plasma and environmental sodium concentration when salinity is increased, no such correlation is apparent after hypophysectomy and/or prolactin treatment in sea water. The physiological meaning of prolactin secretion in sea water is discussed.

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Nous remercions bien vivement le National Institute of Health de Bethesda, Endocrinology Study Section, qui nous a fourni gracieusement la prolactine utilisée dans cette expérience, Mme Martin qui a pratiqué les hypophysectomies, Melle S. Warrot qui a effectué les dosages des electrolytes, et Melle J. Olivereau pour la vérification des hypophysectomies.