Étude du phénomène de l’induction de facteurs bactériolytiques chez les lépidoptères: Inhibition de la production du lysozyme chez les larves deGalleria mellonella [Lep.: Pyralidae] par l’Actinomycine D et la Cycloheximide

Résumé L’introduction de corps étrangers dans les larves de lépidoptères entra?ne une augmentation parfois considérable du taux de lysozyme dans l’hémolymphe. L’efficacité inductrice de diverses substances varie dans de larges mesures. L’action de l’Actinomycine D et de la Cycloheximide sur la production du lysozyme induit a été recherchée chez des larves deGalleria mellonella L. recevant un stimulus peu spécifique (chlorure de sodium) ou plus spécifique (Micrococcus luteus vivants). L’action de ces inhibiteurs sur la quantité de lysozyme présente dans l’hémolymphe 24 h après induction, indique que les variations du taux de l’enzyme sont sous le contr?le d’un mécanisme unique indépendant de la spécificité des stimuli inducteurs. L’augmentation du taux de lysozyme chez les larves deG. mellonella induites, fait suite à une synthèse protéique et non à la libération d’enzyme préformé.

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Summary Foreign bodies introduced into lepidopteran larvae induce an increase, often considerable, in amount of lysozyme in the hemolymph. The efficiency of various substances to elicit the release of lysozyme in the larvae varies to a great extent. The effect of Actinomycin D and Cycloheximide introduced in theGalleria mellonella L. larvae stimulated to produce lysozyme by injection of saline or liveMicrococcus luteus was studied. The action of these metabolic inhibitors on the quantity of lysozyme in the hemolymph, 24 h after injection of the inducers, showed that the variations of the amount of the enzyme are under the control of only one mechanism which is not affected by the nature of the inducers. The increase in lysozyme amount of the hemolymph of the inducedG. mellonella larvae is due to the protein synthesis; it does not result from the release of a preformed enzyme as it was demonstrated in other animal species.

     

Expression of Cytoplasmic Antigens Linked to Orthokeratosis During the Development of Parakeratosis in Newborn Mouse Tail Epidermis

Abstract. An unusual example of two different types of epidermal differentiation occurs side by side in adult mouse tail. The neonate shows only orthokeratotic differentiation, but develops parakeratotic scales in precise patterns over the first two weeks of life, retaining orthokeratotic differentiation at the necks of hair follicles. Certain human IgG antibodies from patients receiving bone marrow transplants bind only to cytoplasmic components of orthokeratotic epithelium. As markers of orthokeratotic differentiation in indirect immunofluorescent studies, these antibodies allowed the timing and location of the change in epidermal differentiation. A specific loss of 'orthokeratotic' antigens in the natural switch from orthokeratosis to parakeratosis was demonstrated. The sequence of the orthokeratotic antigens disappearance suggested that the switch to parakeratotic differentation occurred at a supra-basal level.     

Discovery and structure-guided drug design of inhibitors of 11β-hydroxysteroid-dehydrogenase type I based on a spiro-carboxamide scaffold

Spiro-carboxamides were identified as inhibitors of 11β-hydroxysteroid-dehydrogenase type 1 by high-throughput screening. Structure-based drug design was used to optimise the initial hit yielding a sub-nanomolar IC₅₀ inhibitor (0.5 nM) on human 11β-HSD1 with a high binding efficiency index (BEI of 32.7) which was selective against human 11β-HSD2 (selectivity ratio > 200000).     

Winter host exploitation influences fitness traits in a parasitoid

Organisms can either evade winter's unfavourable conditions by migrating or diapausing, or endure them and maintain their activities. When it comes to foraging during winter, a period of scarce resources, there is strong selective pressure on resource exploitation strategy. Generalist parasitoids are particularly affected by this environmental constraint, as their fitness is deeply linked to the profitability of the available hosts. In this study, we considered a cereal aphid–parasitoid system and investigated (1) the host–parasitoid community structure, host availability, and parasitism rate in winter, (2) the influence of host quality in terms of species and instars on the fitness of the aphid parasitoid Aphidius rhopalosiphi De Stefani‐Perez (Hymenoptera: Braconidae: Aphidiinae), and (3) whether there is a detectable impact of host fidelity on parasitism success of this parasitoid species. Host density was low during winter and the aphid community consisted of the species Rhopalosiphum padi L. and Sitobion avenae Fabricius (both Hemiptera: Aphididae), both parasitized by A. rhopalosiphi at non‐negligible rates. Aphidius rhopalosiphi produced more offspring when parasitizing R. padi compared with S. avenae, whereas bigger offspring were produced when parasitizing S. avenae. Although aphid adults and old larvae were significantly larger hosts than young larvae, the latter resulted in higher emergence rates and larger parasitoids. No impact of host fidelity on emergence rates or offspring size was detected. This study provides some evidence that winter A. rhopalosiphi populations are able to take advantage of an array of host types that vary in profitability, indicating that host selectivity may drop under winter's unfavourable conditions.     

Exopolysaccharides produced by Lactobacillus plantarum: technological properties,biological activity,and potential application in the food industry

Some lactic acid bacteria are capable of producing capsular or extracellular polysaccharides, with desirable technological properties and biological activities. Such polysaccharides produced by lactic acid bacteria are called exopolysaccharides and can be used to alter rheological properties, acting in processes involving viscosity, emulsification, and flocculation, among others. They may also be involved in prebiotic, probiotic, and biological activities, as well as having potential application in the food industry. In this mini-review, the objectives were to present some beneficial properties of exopolysaccharides (EPS) produced by Lactobacillus plantarum that have not been commercially explored. For that, the article focused to summarize revision of current publications within the following topics: (1) rheological properties, (2) prebiotic properties, (3) biological activities, and (4) potential application in the food industry. EPS produced by Lb. plantarum can be used as gelling agent, emulsifier, or stabilizer for food products. The glucan nature of the produced EPS enhances probiotic properties of this LAB species. Lactobacillus plantarum EPS has antioxidant, antibiofilm, and antitumor activities. Finally, there is an improvement in texture of fermented food products where Lb. plantarum is used as starter culture which is related to EPS production in situ. Therefore, EPS produced by Lb. plantarum have important and desirable properties to be explored for several applications, including health and food areas.     

Sulfated HNK-1 epitope in developing and mature kidney: a new marker for thin ascending loop of Henle and tubular injury in acute tubular necrosis.

The HNK-1 carbohydrate epitope is a 3-sulfo-glucuronyl residue attached to lactosamine structures on glycoproteins, proteoglycans, or glycolipids mostly expressed in the nervous system. Here, using monoclonal antibodies against the sulfated HNK-1 carbohydrate epitope, we first examined its distribution in developing and adult kidneys, then its expression in kidneys with tubular necrosis and renal neoplasms. This HNK-1 epitope was expressed in the human, rabbit, and rat, but not mouse kidney. It was detected within a subset of epithelial cells in the renal vesicle and in comma- and S-shaped bodies during early stages of nephrogenesis. In ureteral bud derivatives, the epitope was present transiently in the area where the collecting duct fused with the nephron. In the adult kidney, expression of the HNK-1 epitope became mainly restricted to the thin ascending loop of Henle where this epitope was carried by heparan- and chondro-proteoglycan. In pathological conditions, HNK-1 epitope expression increased dramatically in proximal epithelial tubule cells in kidneys with acute tubular necrosis. In tumors, the HNK-1 epitope was expressed in the epithelial component of nephroblastomas and in a subgroup of papillary renal cell carcinomas. These data suggest that molecules carrying the sulfated HNK-1 carbohydrate epitope may play an important role in critical stages of renal development and in the physiology of thin ascending loop of Henle.