Inter‐individual variation in honey bee dance intensity correlates with expression of the foraging gene

Individual behavioural differences in responding to the same stimuli is an integral part of division of labour in eusocial insect colonies. Amongst honey bee nectar foragers, individuals strongly differ in their sucrose responsiveness, which correlates with strong differences in behavioural decisions. In this study, we explored whether the mechanisms underlying the regulation of foraging are linked to inter‐individual differences in the waggle dance activity of honey bee foragers. We first quantified the variation in dance activity amongst groups of foragers visiting an artificial feeder filled consecutively with different sucrose concentrations. We then determined, for these foragers, the sucrose responsiveness and the brain expression levels of three genes associated with food search and foraging; the foraging gene Amfor, octopamine receptor gene AmoctαR1 and insulin receptor AmInR‐2. As expected, foragers showed large inter‐individual differences in their dance activity, irrespective of the reward offered at the feeder. The sucrose responsiveness correlated positively with the intensity of the dance activity at the higher reward condition, with the more responsive foragers having a higher intensity of dancing. Out of the three genes tested, Amfor expression significantly correlated with dance activity, with more active dancers having lower expression levels. Our results show that dance and foraging behaviour in honey bees have similar mechanistic underpinnings and supports the hypothesis that the social communication behaviour of honey bees might have evolved by co‐opting behavioural modules involved in food search and foraging in solitary insects.     

Adiponectin Enhances the Responsiveness of the Olfactory System

The peptide hormone adiponectin is secreted by adipose tissue and the circulating concentration is reversely correlated with body fat mass; it is considered as starvation signal. The observation that mature sensory neurons of the main olfactory epithelium express the adiponectin receptor 1 has led to the concept that adiponectin may affect the responsiveness of the olfactory system. In fact, electroolfactogram recordings from olfactory epithelium incubated with exogenous adiponectin resulted in large amplitudes upon odor stimulation. To determine whether the responsiveness of the olfactory sensory neurons was enhanced, we have monitored the odorant-induced expression of the immediate early gene Egr1. It was found that in an olfactory epithelium incubated with nasally applied adiponectin the number of Egr1 positive cells was significantly higher compared to controls, suggesting that adiponectin rendered the olfactory neurons more responsive to an odorant stimulus. To analyze whether the augmented responsiveness of sensory neurons was strong enough to elicit a higher neuronal activity in the olfactory bulb, the number of activated periglomerular cells of a distinct glomerulus was determined by monitoring the stimulus-induced expression of c-fos. The studies were performed using the transgenic mOR256-17-IRES-tauGFP mice which allowed to visualize the corresponding glomerulus and to stimulate with a known ligand. The data indicate that upon exposure to 2,3-hexanedione in adiponectin-treated mice the number of activated periglomerular neurons was significantly increased compared to controls. The results of this study indicate that adiponectin increases the responsiveness of the olfactory system, probably due to a higher responsiveness of olfactory sensory neurons.     

Prostaglandin F2 alpha increases responsiveness of pulmonary airways in dogs

We studied the effect of prostaglandin F2 alpha (PGF2 alpha) on the responsiveness of pulmonary airways in dogs. Airway responsiveness was assessed by determining the bronchoconstrictor response to increasing concentrations of acetylcholine aerosol delivered to the airways. In each of five dogs, we determined responsiveness during treatment with physiologic saline, histamine, or PGF2 alpha aerosols. The doses of histamine and PGF2 alpha were determined by establishing the largest dose of each which could be given to the dog without causing bronchoconstriction (subthreshold doses). We found that airway responsiveness was not significantly different during histamine treatment than after saline, however, responsiveness increased during treatment with PGF2 alpha. In addition, the hyperresponsiveness induced by PGF2 alpha was prevented by pretreatment with the ganglion blocking drug hexamethonium (5 mg/kg given intravenously). The results show that PGF2 alpha specifically increases the responsiveness of pulmonary airways in doses that do not cause bronchoconstriction, and suggest that the hyperresponsiveness involves a neural mechanism such as increased responsiveness of airway sensory nerves.     

The response of recombinant inbred strains of mice to bacterial lipopolysaccharides.

Fourteen recombinant inbred strains of mice have been produced by the inbreeding of the F2 generation of a cross between C57BL/6J and C3H/HeJ progenitor mice. The responses of these BXH strains to bacterial lipopolysaccharides (LPS) have been characterized. Four BXH strains are high LPS responders and nine strains are low LPS responders. One BXH strain shows intermediate responsiveness which may reflect residual heterozygosity. F1 hybrid mice from low x high responder strains were intermediate in their response to LPS suggesting additive genetic control. The LPS responses in backcross mice from the F1 x low LPS responders showed segregation consistent with LPS responsiveness being determined by a single gene. In 13/14 BXH strains, there was concordant inheritance of LPS responsiveness and the major urinary protein locus Mup-1b. The association of the expression of the Mup-1 alleles with LPS responsiveness in the BXH strains suggests that the defective LPS response gene in C3H/HeJ mice is located on chromosome 4.     

Responsiveness to Retinoic Acid Changes during Chondrocyte Maturation

We previously showed that retinoic acid (RA) participates in the regulation of chondrocyte maturation during endochondral ossification, a process involving multiple developmental stages. To assess whether the responsiveness to RA treatment changes during chondrocyte maturation, immature chondrocytes were isolated from the caudal portion of Day 18-19 chick embryo sterna, a portion that remains cartilaginous through early postnatal life but ossifies with age. The immature cells were allowed to reach different stages of maturation by growth for different time in culture. Progression by the cells toward the mature phenotype during culture was confirmed by increases in average cell diameter, proteoglycan synthesis, and alkaline phosphatase (APase) activity. When developmentally immature passage 0 (PO) cultures were treated with RA (10-100 nM) for 72 h, the cells readily became fibroblastic, reduced drastically their proteoglycan synthesis, and failed to activate type X collagen gene expression. When older cultures (P1 and P2) were treated with RA, the cells acquired a characteristic epithelioid shape and increased their APase activity. Moreover, 5-10% of P1 cells and 20-25% of P2 cells activated type X collagen synthesis in response to RA. RA treatment markedly induced expression of the gene encoding the β isoform of retinoic acid receptor (RARβ) and also provoked a moderate 2.5-fold increase in RARα gene expression. A similar change in responsiveness to RA was observed during maturation in vivo. Chondrocytes were isolated from the cephalic portion of Day 10, 11, 13, and 16 chick embryo sterna, and were treated with different doses of RA (10-100 nM) for 72 h. The cells from the Day 10 sternum failed to activate type X collagen gene expression in response to RA. In contrast, with increasing age of the embryos, an increasing fraction of cells induced type X collagen gene expression in response to RA. We conclude that responsiveness to RA changes during the early stages of chondrocyte maturation and that maturation depends on interactions between exogenous retinoids and the endogenous developmental program of chondrocytes.     

Studies of the relationship between adenosine deaminase and immune function.

The relationship between adenosine deaminase deficiency and immunologic responsiveness was studied in mice treated in vivo with deoxycoformycin to produce very low levels of adenosine deaminase activity in tissues. Effects of such treatment on thymocyte response to concanavalin A in vitro and on mixed cultures of splenic cells were determined. Under the conditions used, inhibition of adenosine deaminase by deoxycoformycin had no effect on the viability or responsiveness of either thymocytes or splenic cells.     

Physiological and genetic correlates of boldness: characterising the mechanisms of behavioural variation in rainbow trout, Oncorhynchus mykiss

Bold, risk-taking animals have previously been putatively linked with a proactive stress coping style whereas it is suggested shyer, risk-averse animals exhibit a reactive coping style. The aim of this study was to investigate whether differences in the expression of bold-type behaviour were evident within and between two lines of rainbow trout, Oncorhynchus mykiss, selectively bred for a low (LR) or high (HR) endocrine response to stress, and to link boldness and stress responsiveness with the expression of related candidate genes. Boldness was determined in individual fish over two trials by measuring the latency to approach a novel object. Differences in plasma cortisol concentrations and the expression of eight novel candidate genes previously identified as being linked with divergent behaviours or stress were determined. Bold and shy individuals, approaching the object within 180 s or not approaching within 300 s respectively, were evident within each line, and this was linked with activity levels in the HR line. Post-stress plasma cortisol concentrations were significantly greater in the HR line compared with the LR line, and six of the eight tested genes were upregulated in the brains of LR fish compared with HR fish. However, no direct relationship between boldness and either stress responsiveness or gene expression was found, although clear differences in stress physiology and, for the first time, gene expression could be identified between the lines. This lack of correlation between physiological and molecular responses and behavioural variation within both lines highlights the complexity of the behavioural-physiological complex.     

Complement factor B gene regulation: synergistic effects of TNF-alpha and IFN-gamma in macrophages

Complement factor B (Bf) plays an important role in activating the alternative complement pathway. The inflammatory cytokines, in particular TNF-alpha and IFN-gamma, are critical in the regulation of Bf gene expression in macrophages. In this study, we investigated the mechanisms of Bf gene regulation by TNF-alpha and IFN-gamma in murine macrophages. Northern analysis revealed that Bf mRNA expression was synergistically up-regulated by TNF-alpha and IFN-gamma in MH-S cells. Truncations of the 5' Bf promoter identified a region between -556 and -282 bp that mediated TNF-alpha responsiveness as well as the synergistic effect of TNF-alpha and IFN-gamma on Bf expression. Site-directed mutagenesis of a NF-kappaB-binding element in this region (-433 to -423 bp) abrogated TNF-alpha responsiveness and decreased the synergistic effect of TNF-alpha and IFN-gamma on Bf expression. EMSAs revealed nuclear protein binding to this NF-kappaB cis-binding element on TNF-alpha stimulation. Supershift analysis revealed that both p50 and p65 proteins contribute to induction of Bf by TNF-alpha. An I-kappaB dominant negative mutant blocked Bf induction by TNF-alpha and reduced the synergistic induction by TNF-alpha and IFN-gamma. In addition, the proteasome inhibitor MG132, which blocks NF-kappaB induction, blocked TNF-alpha-induced Bf promoter activity and the synergistic induction of Bf promoter activity by TNF-alpha and IFN-gamma. LPS was found to induce Bf promoter activity through the same NF-kappaB cis-binding site. These findings suggest that a NF-kappaB cis-binding site between -433 and -423 bp is required for TNF-alpha responsiveness and for TNF-alpha- and IFN-gamma-stimulated synergistic responsiveness of the Bf gene.     

Activity of protein kinase A and gustatory responsiveness in the honey bee (Apis mellifera L.)

The cAMP-dependent protein kinase A is involved in the induction of long-term memory and habituation in the bee. Gustatory responsiveness correlates strongly with associative and non-associative learning in bees. We tested whether protein kinase A activity in the antennal lobes correlates with gustatory responsiveness. Thirty minutes after feeding, bees with high gustatory responsiveness had a significantly higher protein kinase A activity than bees with low responsiveness. Ninety minutues after feeding, when gustatory responsiveness had increased in initially unresponsive bees, no changes in protein kinase A activity were found. We also tested time-dependent effects of protein kinase A activator and protein kinase A inhibitor on gustatory responsiveness. Injection of the protein kinase A activator adenosine 3'5'-cyclic monophosphate 8-bromo-sodium salt or of the protein kinase A inhibitor KT 5720 did not affect gustatory responsiveness within the first 4 h after treatment. Feeding of adenosine 3'5'-cyclic monophosphate 8-bromo-sodium salt over 4 days increased gustatory responsiveness in newly emerged bees and adult foragers. These results enable us to distinguish between two different forms of gustatory responsiveness: basal and transient gustatory responsiveness. Basal gustatory responsiveness correlates with protein kinase A activity and can only be modulated in the range of several days. Transient gustatory responsiveness appears to be independent of protein kinase A activity and can be modulated in the range of minutes to hours.     

Tissue-specific enhancer of the human glycoprotein hormone alpha-subunit gene: dependence on cyclic AMP-inducible elements.

We identified and characterized elements which confer tissue specificity and cyclic AMP (cAMP) responsiveness to the human glycoprotein alpha-subunit gene. An enhancer containing an 18-base-pair repeat conferred cAMP responsiveness in a non-tissue-specific fashion. DNase I protection assays revealed DNA-binding factors that bound to this element in both placental and nonplacental cells. It also enhanced the alpha-subunit promoter in a tissue-specific manner but had a negligible effect on a heterologous promoter. A unique element found upstream of this enhancer had no independent activity but, in combination with the cAMP-responsive enhancer, distinctly increased the tissue-specific activity of both the alpha-subunit promoter and a heterologous promoter. A factor that bound to this upstream element was found in placental but not nonplacental cells. We conclude that this novel element acts, perhaps through a specific trans-acting factor, in concert with a cAMP-responsive enhancer to confer tissue specificity to the alpha-subunit gene.