On the immature stages of some Merodontini hoverflies (Diptera: Syrphidae) from Europe and Africa.

The genera Eumerus and Merodon (Syrphidae: Merodontini) form together the most speciose grouping of hoverflies in the Palaearctic Region. However, little is known about the morphology and biology of their larvae. The few larvae of Eumerus and Merodon that have been uncovered are phytophagous in underground organs of plants (some Eumerus and all Merodon) or saprophagous in a variety of plants' parts (the reminder of Eumerus). In this study, the second larval stage (L2) of Eumerus lyneborgi Ricarte & Hauser, 2020 and both the larva (L2) and puparium of Merodon constans (Rossi, 1794) are described for the first time. Larvae of E. lyneborgi were found in a decaying stem of Cyphostemma juttae (Dinter & Gilg) Desc., 1960 (Vitaceae) in Namibia (Africa), while larvae of M. constans were collected in bulbs of Leucojum vernum Linnaeus, 1753, (Amaryllidaceae) in France (Europe). Morphology of the immature forms was studied by observation and imaging with stereomicroscopy and scanning electron microscopy. The head skeleton of E. lyneborgi larvae was found to be of the filter feeding type, i.e., in accordance with a saprophagous trophic regime, while that of M. constans was typically phytophagous. Variability in certain characters of the M. constans early stages is described and discussed in relation to the adult form and molecular information published in literature. An updated identification key to all known third larval stages/puparia of Merodon is provided.

A large-scale dataset reveals taxonomic and functional specificities of wild bee communities in urban habitats of Western Europe.

Wild bees are declining, mainly due to the expansion of urban habitats that have led to land-use changes. Effects of urbanization on wild bee communities are still unclear, as shown by contrasting reports on their species and functional diversities in urban habitats. To address this current controversy, we built a large dataset, merging 16 surveys carried out in 3 countries of Western Europe during the past decades, and tested whether urbanization influences local wild bee taxonomic and functional community composition. These surveys encompassed a range of urbanization levels, that were quantified using two complementary metrics: the proportion of impervious surfaces and the human population density. Urban expansion, when measured as a proportion of impervious surfaces, but not as human population density, was significantly and negatively correlated with wild bee community species richness. Taxonomic dissimilarity of the bee community was independent of both urbanization metrics. However, occurrence rates of functional traits revealed significant differences between lightly and highly urbanized communities, for both urbanization metrics. With higher human population density, probabilities of occurrence of above-ground nesters, generalist and small species increased. With higher soil sealing, probabilities of occurrence of above-ground nesters, generalists and social bees increased as well. Overall, these results, based on a large European dataset, suggest that urbanization can have negative impacts on wild bee diversity. They further identify some traits favored in urban environments, showing that several wild bee species can thrive in cities.

Compensatory recruitment allows amphibian population persistence in anthropogenic habitats.

Habitat anthropization is a major driver of global biodiversity decline. Although most species are negatively affected, some benefit from anthropogenic habitat modifications by showing intriguing life-history responses. For instance, increased recruitment through higher allocation to reproduction or improved performance during early-life stages could compensate for reduced adult survival, corresponding to "compensatory recruitment". To date, evidence of compensatory recruitment in response to habitat modification is restricted to plants, limiting understanding of its importance as a response to global change. We used the yellow-bellied toad (Bombina variegata), an amphibian occupying a broad range of natural and anthropogenic habitats, as a model species to test for and to quantify compensatory recruitment. Using an exceptional capture-recapture dataset composed of 21,714 individuals from 67 populations across Europe, we showed that adult survival was lower, lifespan was shorter, and actuarial senescence was higher in anthropogenic habitats, especially those affected by intense human activities. Increased recruitment in anthropogenic habitats fully offset reductions in adult survival, with the consequence that population growth rate in both habitat types was similar. Our findings indicate that compensatory recruitment allows toad populations to remain viable in human-dominated habitats and might facilitate the persistence of other animal populations in such environments.

Perilipin 1 ablation in mice enhances lipid oxidation during exercise and does not impair exercise performance.

Perilipin 1 is involved in the control of adipose tissue triacylglycerol hydrolysis. Its ablation in mice decreases fat mass and induces a partial resistance to diet-induced and genetic obesity. However, the consequences of perilipin 1 invalidation on energy balance are not fully defined. Moreover, the impact of perilipin 1 ablation on exercise performance and on fatty acids mobilization and utilization during exercise has not been studied. We compared energy balance (food intake, energy expenditure, spontaneous physical activity) and response to exercise of Plin1(-/-) and wild-type mice receiving a chow diet. The Plin1(-/-) mice had less fat, comparable food intake, comparable or slightly decreased energy expenditure, and no change in spontaneous physical activity. Mean 24-hour respiratory quotient was slightly lower, suggesting enhanced fatty acid oxidation. Exercise performance (both acute and endurance) was not impaired. Changes in nonesterified fatty acid levels during exercise were comparable, showing that triacylglycerol mobilization was unimpaired. Oxygen consumption increased faster (both tests) and to higher values (acute exercise) in Plin1(-/-) mice. Respiratory quotient increased during both types of exercise in Plin1(-/-) and control mice, but less in Plin1(-/-) mice. These lower respiratory quotient values show that Plin1(-/-) mice rely more on fatty acid oxidation during exercise. This is probably related to an overexpression in liver and muscle of genes for fatty acids oxidation. Perilipin 1 ablation has limited consequences on energy balance. It does not impair exercise performance; fatty acids mobilization during exercise is not impaired, whereas their oxidation is enhanced.

Increased atherosclerosis in mice deficient in perilipin1.

BACKGROUND: Perilipin1, a lipid droplet associated protein has an important role in the regulation of lipolysis and lipid storage in adipocytes. Perilipin1 is also expressed in foam cells of atheroma plaques and could therefore play a role in the accumulation of lipids in arterial wall and in the development of atherosclerosis. The aim of the study was to investigate this possible role of perilipin1 in atherogenesis. METHODS: Mice deficient in perilipin1 (Plin1-/-) were crossed with Ldlr-/- mice. Ldlr-/- and Plin1-/- Ldlr-/- mice received an atherogenic diet during 10 or 20 weeks. Blood pressure and plasma lipids concentrations were measured. Aortas were collected at the end of the atherogenic diet periods for quantification of atheroma lesions (en face method), histological and immunohistological studies RESULTS: Ldlr-/- and Plin1-/- Ldlr-/- mice had comparable blood pressure and plasma lipids levels. Plin1-/- Ldlr-/- mice had a lower body weight and decreased adiposity. The atherosclerotic lesion area in Plin1-/-Ldlr-/- mice was moderately increased after 10 weeks of atherogenic diet (ns) and significantly higher after 20 weeks (p < 0.01). Histology of atheroma plaques was comparable with no sign of increased inflammation in Plin1-/- Ldlr-/- mice. CONCLUSION: Perilipin1 ablation in mice results in increased atherosclerosis independently of modifications of risk factors such as raised blood pressure or plasma lipids levels. These data strongly support an atheroprotective role for perilipin1.

Conditional inactivation of TGF-ß type II receptor in smooth muscle cells and epicardium causes lethal aortic and cardiac defects.

To understand the role of TGF-ß signaling in cardiovascular development, we generated mice with conditional deletion of the TGF-ß type II receptor (TßRII) gene (Tgfbr2) in cells expressing the smooth muscle cell-specific protein SM22α. The SM22α promoter was active in tissues involved in cardiovascular development: vascular smooth muscle cells (VSMCs), epicardium and myocardium. All SM22-Cre(+/-)/Tgfbr2 (flox/flox) embryos died during the last third of gestation. About half the mutant embryos exhibited heart defects (ventricular myocardium hypoplasia and septal defects). All mutant embryos displayed profound vascular abnormalities in the descending thoracic aorta (irregular outline and thickness, occasional aneurysms and elastic fiber disarray). Restriction of these defects to the descending thoracic aorta occurred despite similar levels of Tgfbr2 invalidation in the other portions of the aorta, the ductus arteriosus and the pulmonary trunk. Immunocytochemistry identified impairment of VSMC differentiation in the coronary vessels and the descending thoracic aorta as crucial for the defects. Ventricular myocardial hypoplasia, when present, was associated to impaired α-SMA differentiation of the epicardium-derived coronary VSMCs. Tgfbr2 deletion in the VSMCs of the descending thoracic aorta diminished the number of α-SMA-positive VSMC progenitors in the media at E11.5 and drastically decreased tropoelastin (from E11.5) and fibulin-5 (from E.12.5) synthesis and/or deposition. Defective elastogenesis observed in all mutant embryos and the resulting dilatation and probable rupture of the descending thoracic aorta might explain the late embryonic lethality. To conclude, during mouse development, TGF-ß plays an irreplaceable role on the differentiation of the VSMCs in the coronary vessels and the descending thoracic aorta.

Density-dependent shift of transforming growth factor-beta-1 from inhibition to stimulation of vascular smooth muscle cell growth is based on unconventional regulation of proliferation, apoptosis and contact inhibition.

BACKGROUND: TGF-beta shifts from inhibition to stimulation of vascular smooth muscle cell (vSMC) growth when cell density increases. How proliferation and apoptosis contribute to this shift is still unknown. METHODS: In sparse and confluent V8 vSMC treated or not with TGF-beta(1) (1 ng/ml) for 3 days, cell number, mitotic activity, cell-cycle-regulatory protein levels, caspase-3 and phosphoinositide 3-kinase (PI3-K) activities were studied. RESULTS: In TGF-beta(1)-treated cells, (i) the growth curve rose constantly compared to controls, reaching post-confluent densities; (ii) mitotic activity, which was constant at all cell densities, was lower than in sparse but higher than in contact-inhibited control cells, and (iii) apoptosis occurred at sparse densities only. The mechanism of proliferation control by TGF-beta(1) was very unconventional in V8 vSMCs: (i) p15(INK4b) and cyclin D levels were similar in cells treated or not with TGF-beta(1), and (ii) p27(Kip1) levels remained very low even at high densities while cyclin E levels were not markedly decreased. TGF-beta(1)-induced apoptosis in sparse cultures and its reversal in dense cultures were inversely correlated to PI3-K activation. CONCLUSIONS: TGF-beta(1) slowed sparse V8 vSMC growth by inhibiting proliferation and inducing apoptosis. TGF-beta(1)-treated confluent vSMCs escaped contact inhibition and kept growing through unconventional regulation of p27(Kip1), cyclin E and suppression of apoptosis.

Expression of the TGF-beta/BMP inhibitor EVI1 in human dental pulp cells.

Members of the TGF-beta/BMP family of growth factors induce odontoblast differentiation and reparative dentin synthesis, and their use has been proposed to stimulate pulp healing during dental therapeutics in human. However, factors that modulate TGF-beta and/or BMP signalling during odontoblast differentiation and physiology remain largely unknown. To identify them, we compared expression profiles of TGF-beta/BMP-related genes in pulp fibroblast- and odontoblast-like cells cultured from human dental pulp explants using cDNA gene arrays. We evidenced that the gene encoding ecotropic viral integration site-1 (EVI1), a transcription factor that inhibits TGF-beta/BMP signalling, was under-expressed in odontoblast-like cells. This result was verified by real-time PCR and, at the protein level, by immunohistochemistry. In vivo, real-time PCR analysis revealed that EVI1 was expressed in the dental pulp, at a level similar to brain, but lower than in lung, kidney or trachea. The protein was localized in dental pulp samples in pulp core and subodontoblast cells. Staining intensity progressively decreased from the radicular to the coronal pulp where EVI1 staining was almost undetectable in odontoblasts. Our data suggest that fine regulation of the EVI1 level in the human dental pulp might be important in the TGF-beta/BMP-induced modulation of dental pulp cell kinetics and/or odontoblast differentiation.

Temporal pattern of the induction of SF-1 gene expression by the signal transduction pathway involving 3',5'-cyclic adenosine monophosphate.

The objective of our study was to investigate the effect of stimulation of the cAMP-dependent pathway on the expression of an orphan nuclear receptor, SF-1/Ad4BP in mouse adrenal tumour, Y-1 cells in culture. We evaluated the temporal pattern of the effects of corticotropin (ACTH) and the adenylyl cyclase activator forskolin on the level of SF-1 mRNA, and compared the time course of induction of SF-1 with that of CYP11A1. Forskolin, corticotropin and 8-Br-cAMP significantly elevated the level of the SF-1 transcript, after 1.5 h of incubation, with a concomitant increase of SF-1 protein level, observed after 6 h. The CYP11A1 transcript increased gradually over the incubation period, and reached the maximal level after 12 to 24 h. The steady-state level of the SF-1 transcript was unaffected by forskolin when the cells were incubated with actinomycin D, indicating that stimulation of the cAMP pathway results in enhanced transcription of the gene. The effect of forskolin was augmented by cycloheximide, suggesting that an inhibitory protein, whose synthesis was inhibited by cycloheximide, could be involved in negative regulation of SF-1 expression. It is concluded that SF-1 expression is positively regulated by the cAMP pathway at the transcriptional level, and can represent the primary event in cAMP-mediated induction of steroid hormone synthesis in Y-1 cells.

A 7.1 kbp beta-myosin heavy chain promoter, efficient for green fluorescent protein expression, probably induces lethality when overexpressing a mutated transforming growth factor-beta type II receptor in transgenic mice.

The roles of transforming growth factor-beta (TGFbeta) in heart or skeletal muscle development and physiology are still the subject of controversies. Our aim was to block, in transgenic mice, the TGFbeta signalling pathway by a dominant negative mutant of the TGFbeta type II receptor fused to the enhanced green fluorescent protein (TbetaRII-KR-EGFP) under the control of a 7.1 kbp mouse beta-myosin heavy chain (betaMHC) promoter to investigate the roles of TGFbeta in the heart and slow skeletal muscles. First, we generated two transgenic lines overexpressing EGFP under the control of the 7.1 kbp betaMHC promoter. In embryos, EGFP was detectable as early as 7.5 days post coitum. In embryos, newborns and adults, EGFP was expressed mainly in the cardiac ventricles and in slow skeletal muscles. EGFP expression was intense in the bladder but weak in the intestines. In contrast to the endogenous betaMHC promoter, the activity of the 7.1 kbp betaMHC promoter in the transgene was not repressed after birth and remained high in adult transgenic mice. We obtained two founders with the transgene comprising the TbetaRII-KR-EGFP sequence under the control of the 7.1 kbp betaMHC promoter. These founders were generated at a very low frequency and expressed barely detectable levels of TbetaRII-KR-EGFP mRNA. Our failure to obtain transgenic lines overexpressing the dominant negative receptor suggests that the blocking of the TGFbeta signalling pathway in the heart and slow skeletal muscles could be embryonically lethal. To conclude, the 7.1 kbp betaMHC promoter directs high levels of transgene expression in the cardiac ventricles and in slow skeletal muscles of the mouse. Analysis of the consequences of the blocking of the TGFbeta signalling pathway in the heart will require the use of tissue specific means of conditional gene invalidation.

Perceptual interactions in odour mixtures: odour quality in binary mixtures of woody and fruity wine odorants.

The qualitative perceptual interactions in three binary mixtures of wine odorants were studied: isoamyl acetate (fruity note)/whisky lactone (woody note), ethyl butyrate (fruity note)/whisky lactone (woody note) and ethyl butyrate (fruity note)/guaiacol (woody note). For each binary mixture, the perceived quality and intensity of 24 stimuli (four supra-threshold concentration levels of each of the two compounds and their 16 possible combinations) were evaluated in five replications by a trained panel of 13 subjects. The application of the Olsson predictive model for odour intensity and quality perception gave quite a good estimation of the evolution of single component identification in the mixture when the intensity proportion of unmixed components varied. However, this model was unable to account for the odour quality dominance in mixtures of iso-intense components. An alternative linear logistic model was proposed to study the qualitative dominance of the woody note in the three mixtures when the perceived intensities of each unmixed compound were equal.

Newborn rabbit responsiveness to the mammary pheromone is concentration-dependent.

The effect of the intensity of odour signals has rarely been investigated in the regulation of odour-guided behaviour in young mammals. This series of experiments used the mammary pheromone (MP) of the female rabbit to assess the influence of stimulus concentration on neonatal pup responsiveness. The MP is a single compound isolated from rabbit milk that releases in pups the typical head searching and oral seizing behaviour. The pups (n = 621) were exposed to graded concentrations of the MP in bioassays varying in stimulus delivery conditions. Experiment 1 demonstrated that in aqueous dilutions the MP efficiently elicits behavioural responses only within a limited range of concentrations (from 2.5 x 10(-9) to 2.5 x 10(-5) g/ml). Experiment 2 yielded the same outcome with highly purified MP delivered in dynamic conditions with a gas chromatograph. Finally, Experiment 3 used deodorized milk as the solvent of the MP; despite this change in the physico-chemical context of stimulation, similar results were reached.

Terminal differentiation of Sol 8 myoblasts is retarded by a transforming growth factor-beta autocrine regulatory loop.

In DM (differentiation medium), Sol 8 myoblasts spontaneously form myotubes and express the betaMHC (beta-myosin heavy chain), their main marker of terminal differentiation. This marker is detectable at 24 h, and increases up to 72 h. Our aim was to define temporal effects of TGFbeta (transforming growth factor beta) on betaMHC expression in Sol 8 cells. TGFbeta1 (1 ng/ml) added at time zero to DM decreased MyoD expression and completely inhibited betaMHC expression in Sol 8 cells. This inhibition of betaMHC expression was progressively lost when TGFbeta1 was added from 8 to 34 h. After 34 h, the cells were irreversibly differentiated, and TGFbeta1 did not inhibit betaMHC accumulation any longer. Two independent approaches showed that a TGFbeta autocrine regulatory loop retarded and partially impaired Sol 8 cell terminal differentiation. First, permanent immunoneutralization of the active TGFbetas released by the cells into DM increased betaMHC levels at 72 h compared with controls. Secondly, a dominant-negative mutant of the TGFbeta type II receptor was overexpressed in Sol 8 cells under the control of the betaMHC promoter. Both the dominant-negative receptor and the betaMHC gene were expressed after 24 h in DM. The delayed blocking of the TGFbeta signalling pathway by the dominant-negative receptor was as effective as permanent immunoneutralization to promote betaMHC expression. To conclude, TGFbeta inhibits Sol 8 cell terminal differentiation within a narrow time interval (24-34 h) that coincides with the onset of betaMHC expression.

Chemical and behavioural characterization of the rabbit mammary pheromone.

Mammals owe part of their evolutionary success to the harmonious exchanges of information, energy and immunity between females and their offspring. This functional reciprocity is vital for the survival and normal development of infants, and for the inclusive fitness of parents. It is best seen in the intense exchanges taking place around the mother's offering of, and the infant's quest for, milk. All mammalian females have evolved behavioural and sensory methods of stimulating and guiding their inexperienced newborns to their mammae, whereas newborns have coevolved means to respond to them efficiently. Among these cues, maternal odours have repeatedly been shown to be involved, but the chemical identity and pheromonal nature of these cues have not been definitively characterized until now. Here we focus on the nature of an odour signal emitted by the female rabbit to which newborn pups respond by attraction and oral grasping, and provide a complete chemical and behavioural description of a pheromone of mammary origin in a mammalian species.

Development and function of the human fetal adrenal cortex.

The development and function of the primate adrenal cortex are characterized by rapid growth, high steroidogenic activity, and a particular morphological appearance. The fetal adrenal glands grow rapidly and exponentially and at term are similar in weight to adult adrenals. From birth to 1 year their mass is reduced as they undergo a process of differentiation. Growth then remains slow until age 7 years. Thereafter, growth accelerates and the adrenals reach adult weight by the end of puberty. In the first trimester of gestation, fetal adrenal growth is thought to be independent of adrenocorticotropic hormone (ACTH), but after 15 weeks, ACTH is absolutely required for normal morphological and functional development. Other factors of fetal and/or placental origin, acting independently of or in conjunction with ACTH, are also required. Basic fibroblast growth factor, epidermal growth factor/transforming growth factor beta, and insulin-like growth factor (IGF)-I and -II, all acting in an autocrine and/or paracrine fashion, have been postulated to stimulate fetal adrenal cell proliferation. Corticotropin-releasing hormone may also play an important role in primate fetal adrenal function, primarily at the end of gestation. Finally, the estrogens are also important in the development of the pituitary-adrenal axis in primates.

Orientation response of newborn rabbits to odours of lactating females: relative effectiveness of surface and milk cues.

To assess temporal and spatial variations in the emission of the odour guiding them to the nipples, we exposed newborn rabbits, Oryctolagus cuniculus, to lactating females in a series of simultaneous olfactory choice tests. They showed a clear preference for females in early, rather than late, lactation, and in the prenursing, rather than postnursing, phase. Furthermore, the female's abdominal, and specifically nipple, regions were more attractive to pups than the back and non-nipple abdominal areas. Finally, the surface odour cues from the abdomen of lactating females were as attractive as the odour of rabbit milk itself. These data suggest that the source of the active compound eliciting preferential orientation is located on the nipple, a site allowing simultaneous evaporation in air and dissolution in milk. Copyright 2001 The Association for the Study of Animal Behaviour.