HIBERNATION CHEZ TROIS ESPÈCES DE MÉTOPIINES: HYMENOPTERA,ICHNEUMONIDAE

Résumé Les conditions de l'hibernation sont étudiées chez les trois espèces de Métopiines Chorinaeus funebris Gravenhorst, Triclistus podagricus Gravenhorst et Triclistus pygmaeus Cresson. Ces espèces hibernent à des stades de développement compris entre l'éonymphe et l'adulte non émergé (Tableau I). La durée de l'incubation complémentaire après réactivation par le froid à 2^o varie entre 10 et 30 jours en moyenne (Tableaux II, IV et V). Chez T. podagricus et T. pygmaeus, on a observé également des émergences d'adultes avant l'hiver (Tableau III). I1 semble que T. podagricus ne parvienne au stade d'imago hibernant qu'après une baisse de la température d'élevage. Aucune souche dépourvue de diapause n'a pu être créée, mais pour les trois espèces, deux générations annuelles seraient possibles sous conditions contrôlées. Enfin, l'utilisation éventuelle de T. pygmaeus pour une lutte biologique contre Zeiraphera diniana Guénée est évoquée.

---

Summary The conditions of hibernation have been investigated in the three metopiine species Chorinaeus funebris, Triclistus podagricus and Triclistus pygmaeus, all entomophagous on Zeiraphera diniana Guénée (Lepidoptera, Tortricidae) in the Engadine Valley (Switzerland). The hibernating stages are eonymph, pronymph or unemerged adult inside the host pupae (Table I). The length of the complementary incubation after reactivation at 2^o varies between 10–30 days (Tables II, IV and V). A small number of T. podagricus and of T. pygmaeus regularly appear as adults before winter, in rearings of both laboratory and field populations (Table III). It seems that T. podagricus larvae need a reduction in the initial rearing temperature before full development is achieved and the hibernating stage is reached (imago). No strain without diapause could be obtained for any of the three species, but the rearing of two annual generations under controlled conditions is possible in the laboratory. The eventual use of T. pygmaeus as a control agent against Z. diniana is discussed.

     

Biology of Ixodes (Pholeoixodes) hexagonus under laboratory conditions Part II. Effect of mating on feeding and fecundity of females

The effect of mating on the feeding and fecundity ofIxodes (Pholeoixodes) hexagonus females was studied under controlled laboratory conditions of 22–23°C and 98% relative humidity. The feeding period of mated females was 6–15 days and 11–13 days for unmated females. The mean weight of the engorged mated females was 114.84±45.89 mg, whereas, that of the engorged unmated females was significantly lower (80.61±28.84 mg). During the initial slow feeding period, the weight of mated females increased 6.6 times. At the end of the blood feeding, they had increased their initial weight 35.5 times. Unmated females never entered the rapid engorgement phase and up to 12 days of feeding period their mean weight did not increase more than 9.2 times. The pre-oviposition periods of mated and unmated females were 6–15 days and 4–12 days, respectively. The mean of the egg production efficiency was 40.26±12.47% for mated females and 35.68±12.2% for unmated females. The mean of the mass conversion efficiency was 73.6±13.7% for mated females and 66.48 ±16.55% for unmated females. Sixty per cent of the eggs deposited by mated females hatched whereas only 1% of the eggs deposited by unmated females hatched. These results indicate thatI. hexagonus females possess some predisposition for parthenogenesis and only fertility and not fecundity depends on mating.     

A kinetic analysis of hybridoma growth and metabolism in continuous suspension culture on serum-free medium

The steady-state metabolic parameters for a murine hybridoma cell line have been determined in continuous suspension culture over a wide range of dilution rates. Long-term adaption occurred over seven months in culture and resulted in lower glucose consumption rates, reduced lactate production, higher cell viability, and, consequently, growth rates more nearly matching the dilution rate. Antibody production rates decreased over the first two months and then remained stable for at least 75 days. The antibody production rate was not found to be growth associated. Steadystate amino acid uptake rates are presented for a wide range of growth rates.     

Transglutaminase 6: a protein associated with central nervous system development and motor function

Transglutaminases (TG) form a family of enzymes that catalyse various post-translational modifications of glutamine residues in proteins and peptides including intra- and intermolecular isopeptide bond formation, esterification and deamidation. We have characterized a novel member of the mammalian TG family, TG6, which is expressed in a human carcinoma cell line with neuronal characteristics and in mouse brain. Besides full-length protein, alternative splicing results in a short variant lacking the second β-barrel domain in man and a variant with truncated β-sandwich domain in mouse. Biochemical data show that TG6 is allosterically regulated by Ca²⁺ and guanine nucleotides. Molecular modelling indicates that TG6 could have Ca²⁺ and GDP-binding sites related to those of TG3 and TG2, respectively. Localization of mRNA and protein in the mouse identified abundant expression of TG6 in the central nervous system. Analysis of its temporal and spatial pattern of induction in mouse development indicates an association with neurogenesis. Neuronal expression of TG6 was confirmed by double-labelling of mouse forebrain cells with cell type-specific markers. Induction of differentiation in mouse Neuro 2a cells with NGF or dibutyryl cAMP is associated with an upregulation of TG6 expression. Familial ataxia has recently been linked to mutations in the TGM6 gene. Autoantibodies to TG6 were identified in immune-mediated ataxia in patients with gluten sensitivity. These findings suggest a critical role for TG6 in cortical and cerebellar neurons.     

Evolution of transglutaminase genes: identification of a transglutaminase gene cluster on human chromosome 15q15. Structure of the gene encoding transglutaminase X and a novel gene family member, transglutaminase Z

We isolated and characterized the gene encoding human transglutaminase (TG)(X) (TGM5) and mapped it to the 15q15.2 region of chromosome 15 by fluorescence in situ hybridization. The gene consists of 13 exons separated by 12 introns and spans about 35 kilobases. Further sequence analysis and mapping showed that this locus contained three transglutaminase genes arranged in tandem: EPB42 (band 4.2 protein), TGM5, and a novel gene (TGM7). A full-length cDNA for the novel transglutaminase (TG(Z)) was obtained by anchored polymerase chain reaction. The deduced amino acid sequence encoded a protein with 710 amino acids and a molecular mass of 80 kDa. Northern blotting showed that the three genes are differentially expressed in human tissues. Band 4.2 protein expression was associated with hematopoiesis, whereas TG(X) and TG(Z) showed widespread expression in different tissues. Interestingly, the chromosomal segment containing the human TGM5, TGM7, and EPB42 genes and the segment containing the genes encoding TG(C),TG(E), and another novel gene (TGM6) on chromosome 20q11 are in mouse all found on distal chromosome 2 as determined by radiation hybrid mapping. This finding suggests that in evolution these six genes arose from local duplication of a single gene and subsequent redistribution to two distinct chromosomes in the human genome.     

Major histocompatibility complex diversity influences parasite resistance and innate immunity in sticklebacks

Proteins of the major histocompatibility complex (MHC) play a central role in the presentation of antigens to the adaptive immune system. The MHC also influences the odour-based choice of mates in humans and several animal taxa. It has recently been shown that female three-spined sticklebacks (Gasterosteus aculeatus) aim at a moderately high MHC diversity in their offspring when choosing a mate. Do they optimize the immune systems of their offspring? Using three-spined sticklebacks that varied in their individual numbers of MHC class IIB molecules, we tested, experimentally, whether allelic diversity at the MHC influences parasite resistance and immune parameters. We found that sticklebacks with low MHC diversity suffered more from parasite infection after experimental exposure to Schistocephalus solidus tapeworms and Glugea anomala microsporidians. They also showed the highest proportion of granulocytes and the strongest respiratory burst reaction, which are correlates of innate immunity. This indicates a strong activity of the innate immune system after challenge by parasites when MHC diversity is suboptimal. Individuals with very high allelic diversity at the MHC seemed inferior to those with moderately high diversity. Such a pattern is consistent with theoretical expectations of an optimal balance between the number of recognizable antigens and self-tolerance.     

Detection of kappa and delta opioid receptors in skin--outside the nervous system

Opioid receptors (OR) are widely expressed in the central nervous system (CNS). Opioid antinociception might be initiated by activation of OR outside the CNS, indicating targeting of peripheral OR could be useful in the treatment of chronic pain. This study was designed to detect OR in skin tissues of healthy volunteers at both mRNA and protein levels. Skin samples from 10 healthy individuals were investigated. Total isolated RNAs were reverse transcribed, amplified and quantified by real-time PCR. Tissue and skin fibroblast OR protein was detected by immunohistochemistry, Western blot, and immunofluorescence. All skin tissue samples expressed delta- (DOR) and kappa-OR (KOR) mRNAs. Using immunohistochemistry, DOR and KOR were localized in skin fibroblast-like and mononuclear cells. Skin fibroblasts in culture expressed DOR and KOR mRNA. Using immunofluorescence, both DOR and KOR proteins were expressed predominantly on the cell membrane with minor staining in the cytoplasm. We suggest that enhanced expression of DOR and KOR in skin justifies the exploration of selective novel delta and kappa agonists for local pain treatment.     

High variation in foliage and leaf litter chemistry among 45 tree species of a neotropical rainforest community

Distinct ecosystem level carbon : nitrogen : phosphorus (C : N : P) stoichiometries in forest foliage have been suggested to reflect ecosystem-scale selection for physiological strategies in plant nutrient use. Here, this hypothesis was explored in a nutrient-poor lowland rainforest in French Guiana. Variation in C, N and P concentrations was evaluated in leaf litter and foliage from neighbour trees of 45 different species, and the litter concentrations of major C fractions were also measured. Litter C ranged from 45.3 to 52.4%, litter N varied threefold (0.68-2.01%), and litter P varied seven-fold (0.009-0.062%) among species. Compared with foliage, mean litter N and P concentrations decreased by 30% and 65%, respectively. Accordingly, the range in mass-based N : P shifted from 14 to 55 in foliage to 26 to 105 in litter. Resorption proficiencies indicated maximum P withdrawal in most species, but with a substantial increase in variation in litter P compared with foliage. These data suggest that constrained ecosystem-level C : N : P ratios do not preclude the evolution of highly diversified strategies of nutrient use and conservation among tropical rainforest tree species. The resulting large variation in litter quality will influence stoichiometric constraints within the decomposer food web, with potentially far-ranging consequences on nutrient dynamics and plant-soil feedbacks.