Progressive calibrated pressure device to measure cutaneous blood flow changes to external pressure strain

The present methodological paper describes a simple and useful device for local, external pressure application. The mechanical devices, the difficulties, the time required, the possibilities and limitations of the technique to apply a progressive calibrated pressure and to measure cutaneous blood flow with a laser Doppler probe at the same site are discussed. This technique was used to study the effects of local pressure on the cutaneous blood flow with laser Doppler technique. Use of this protocol has provided evidence for a transient cutaneous vasodilation in the human hand during progressive externally applied pressure strain. Results from our laboratory thus far suggest that this vasodilator response is mediated by small sensory nerve fibres in the skin.     

Poly(I:C) used for human dendritic cell maturation preserves their ability to secondarily secrete bioactive IL-12

Dendritic cells (DC) are professional antigen-presenting cells that play a central role in the control of immunity. Mature DC are characterized by high expression levels of MHC and co-stimulatory molecules, and by the secretion of IL-12, a key cytokine for the priming of cytotoxic T lymphocytes. Here, we have compared different maturation stimuli to reproducibly generate stable mature DC secreting high amounts of bioactive IL-12p70. We have compared soluble human trimeric CD40 ligand (sCD40L) combined with IFN-gamma, poly(I:C), a cocktail of cytokines (IL-1beta, IL-6 and tumor necrosis factor-alpha) with prostaglandin E(2) and lipopolysaccharide. A major concern, however, is whether DC, that have already produced high amounts of IL-12p70 during the maturation step, are still capable of secreting IL-12p70 after in vivo administration at the time of interaction with the targeted T cells. To mimic that situation, mature DC generated by those methods were compared for their ability to secrete IL-12p70 in the absence of IFN-gamma, using sCD40L. We observed a second consistent secretion of bioactive IL-12p70 upon subsequent sCD40L stimulation only when poly(I:C) was used as the maturating agent. Our data suggest that, for clinical use, poly(I:C) may be one of the most appropriate agents to generate stable mature DC. These mature DC might generate in vivo effective immune responses after injection, because they retain the ability to secrete bioactive IL-12 after CD40 ligation.     

Differences between cerebral and cerebellar autoregulation during progressive hypotension in rats

Autoregulation in the brain is essential to the maintenance of perfusion and hence to the normal functioning of the organism in the face of various hemodynamic challenges. The existence of prodromal symptoms preceding fainting suggests that cerebellar autoregulation could be altered earlier than cerebral autoregulation during the development of hypotension. The purpose of this study was to compare cerebral and cerebellar autoregulatory responses to hypotension induced by two rates of hemorrhage 1.5 and 2.0 ml/min. Cortical blood flows were measured simultaneously using laser Doppler flowmetry in rats. With increasing rate of hemorrhage, the kinetics of autoregulation were maintained in the cerebrum, whereas it caused a progressive loss in the efficacy of autoregulation in the cerebellum.     

Cutaneous neurovascular interaction involved in tactile sensation

The sense of touch is one of the most vital; still, it is incompletely understood. We review the afferent function that allows for the relay of sensory information from the periphery (the skin) to the central nervous system. Within this afferent function, we examine the different integrating levels including several candidates for cutaneous transducers, the conduction of the information via the afferent nervous fibres and the transmission of the sensory stimuli to higher brain structures, resulting in the perception of the different senses. We then examine the efferent system that stimulates the skin by secreting neurotransmitters. Finally, we discuss the tools available to study the cutaneous neurovascular interaction and conclude on a novel test that assesses this interaction triggered by the application of a local non noxious pressure (tactile stimulation).     

Preservation of pressure-induced cutaneous vasodilation by limiting oxidative stress in short-term diabetic mice

OBJECTIVE: Pressure-induced vasodilation (PIV) allows skin blood flow to increase in response to locally applied pressure and may be protective against pressure ulcers. We previously showed that PIV was absent in 1-week diabetic mice exhibiting no neuropathy. Our aim was to determine whether the diabetes-induced PIV alteration could be prevented. METHODS AND RESULTS: Diabetic mice received no treatment or a daily treatment with either sorbinil, alagebrium or alpha-lipoic acid (LPA) for 1 week. Laser Doppler flowmetry was used to evaluate PIV as well as endothelium-dependent vasodilation following iontophoretic delivery of acetylcholine (ACh). The effect of each treatment on oxidative stress was examined by plasma 8-isoprostane assay. LPA was the sole treatment to prevent both PIV and ACh vasodilation alterations, with a significant reduction of oxidative stress in diabetic mice. Both PIV and ACh-vasodilation were abolished in LPA-treated diabetic mice following injection of Nomega-nitro-L-arginine (p<0.05). In contrast, alagebrium and sorbinil prevented neither diabetes-induced PIV abolition nor endothelial alteration. CONCLUSIONS: LPA treatment significantly reduced the oxidative stress and was able to preserve endothelial nitric oxide availability in the cutaneous microcirculation and then to preserve the PIV response in diabetic mice. LPA treatment could play a key role in limiting the risk of pressure-induced cutaneous ulcer during diabetes.     

Neonatal ghrelin programs development of hypothalamic feeding circuits

A complex neural network regulates body weight and energy balance, and dysfunction in the communication between the gut and this neural network is associated with metabolic diseases, such as obesity. The stomach-derived hormone ghrelin stimulates appetite through interactions with neurons in the arcuate nucleus of the hypothalamus (ARH). Here, we evaluated the physiological and neurobiological contribution of ghrelin during development by specifically blocking ghrelin action during early postnatal development in mice. Ghrelin blockade in neonatal mice resulted in enhanced ARH neural projections and long-term metabolic effects, including increased body weight, visceral fat, and blood glucose levels and decreased leptin sensitivity. In addition, chronic administration of ghrelin during postnatal life impaired the normal development of ARH projections and caused metabolic dysfunction. Consistent with these observations, direct exposure of postnatal ARH neuronal explants to ghrelin blunted axonal growth and blocked the neurotrophic effect of the adipocyte-derived hormone leptin. Moreover, chronic ghrelin exposure in neonatal mice also attenuated leptin-induced STAT3 signaling in ARH neurons. Collectively, these data reveal that ghrelin plays an inhibitory role in the development of hypothalamic neural circuits and suggest that proper expression of ghrelin during neonatal life is pivotal for lifelong metabolic regulation.