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Background Chemotherapy is effective in metastatic pancreatic adenocarcinoma (mPA), but new approaches are still needed to improve patients' survival and quality of life. We have previously published good efficacy and tolerability results on a sequential treatment strategy of gemcitabine followed by an intensified FOLFIRI (5FU+irinotecan) regimen. In the present study, we evaluated the same sequence but replaced gemcitabine by the new gemcitabine + nab-paclitaxel standard first-line combination. Patients and methods We randomised chemotherapy-naive patients with proven mPA, bilirubin levels ≤1.5 upper limit of normal values and performance status 0–2 to alternately receive gemcitabine + nab-paclitaxel for 2 months then FOLFIRI.3 for 2 months in arm A, or gemcitabine + nab-paclitaxel alone until progression in arm B. The primary objective was to increase the 6-month progression-free survival (PFS) rate from 40% (H0) to 60% (H1); using the binomial exact method, 124 patients were required. Analyses were carried out in preplanned modified intention-to-treat (mITT) and per-protocol (PP) populations. Results Between November 2015 and November 2016, 127 patients were enrolled. Main grade III–IV toxicities (% in arm A/B) were: diarrhoea (12.5/1.7), neutropenia (46.9/31, including febrile neutropenia: 1.6/0), skin toxicity (6.3/13.8), and peripheral neuropathy (6.3/8.6). No toxic deaths occurred. The objective response rate was 40.3% (95% confidence interval [CI]: 28.1–53.6) in arm A and 26.7% (95% CI: 16.1–39.7) in arm B. The primary end-point (6-month PFS rate) was 45.2% [one-sided 95% CI: 34.3–56.4] in arm A and 23.3% in arm B [one-sided 95% CI: 14.3–32.3] in the mITT population. In the PP population, median PFS and OS were 7.6 months and 6 months and 14.5 months and 12.2 months in arm A and B, respectively. Conclusions The FIRGEMAX strategy with gemcitabine + nab-paclitaxel alternating with FOLFIRI.3 every 2 months, appears feasible and effective, with manageable toxicities, in patients able to reach >2mo of treatment. Trial registration information EudraCT: 2014-004449-28: NCT: 0282701.

Recurrent apneas are important causes of hospitalization and morbidity in newborns. Gestational stress (GS) compromises fetal brain development. Maternal stress and anxiety during gestation are linked to respiratory disorders in newborns; however, the mechanisms remain unknown. Here, we tested the hypothesis that repeated activation of the neuroendocrine response to stress during gestation is sufficient to disrupt the development of respiratory control and augment the occurrence of apneas in newborn rats. Pregnant dams were displaced and exposed to predator odor from days 9 to 19 of gestation. Control dams were undisturbed. Experiments were performed on male and female rats aged between 0 and 4 d old. Apnea frequency decreased with age but was consistently higher in stressed pups than controls. At day 4, GS augmented the proportion of apneas with O2desaturations by 12%. During acute hypoxia (12% O2), the reflexive increase in breathing augmented with age; however, this response was lower in stressed pups. Instability of respiratory rhythm recorded from medullary preparations decreased with age but was higher in stressed pups than controls. GS reduced medullary serotonin (5-HT) levels in newborn pups by 32%. Bath application of 5-HT and injection of 8-OH-DPAT [(±)-8-hydroxy-2-di-(n-propylamino) tetralin hydrobromide; 5-HT1Aagonist;in vivo] reduced respiratory instability and apneas; these effects were greater in stressed pups than controls. Sex-specific effects were observed. We conclude that activation of the stress response during gestation is sufficient to disrupt respiratory control development and promote pathological apneas in newborn rats. A deficit in medullary 5-HT contributes to these effects.

The mechanisms underlying the therapeutic function of caffeine on apneas in preterm neonates are not well determined. To better understand these effects, we exposed rat pups from postnatal d 3-12 to chronic intermittent hypoxia (5% O2/100 s every 10 min; 6 cycles/h followed by 1 h at 21% O2, 24 h/d), a model mimicking hypoxemic exposure in apneic neonates. Then, using whole-body plethysmography, we evaluated minute ventilation, apnea frequency, and duration after i.p injection of caffeine citrate (20 mg/kg) or saline under normoxia and in response to either sustained (FiO2 12%, 20 min) or brief (FiO2 5%, 60 s, total 10 episodes of 8 min each) hypoxia. These tests were used to assess peripheral and central components of hypoxic response. The latter also assessed the ventilatory long-term facilitation during recovery (2 h). Caffeine injection increased minute ventilation under baseline and during recovery. This effect was correlated with a decrease in apnea frequency (not duration). On the contrary, caffeine did not change the ventilatory response to sustained or brief hypoxic exposure. These results suggest that the effects of caffeine on apnea depend on increased central normoxic respiratory drive and enhancement of ventilatory long-term facilitation rather than on higher hypoxic ventilatory response.

Ventilatory long-term facilitation (LTF; defined as gradual increase of minute ventilation following repeated hypoxic exposures) is well described in adult mammals and is hypothesized to be a protective mechanism against apnea. In newborns, LTF is absent during the first postnatal days, but its precise developmental pattern is unknown. Accordingly, this study describes this pattern of postnatal development. Additionally, we tested the hypothesis that chronic intermittent hypoxia (CIH) from birth alters this development. LTF was estimated in vivo using whole body plethysmography by exposing rat pups at postnatal days 1, 4, and 10 (P1, P4, and P10) to 10 brief hypoxic cycles (nadir 5% O2) and respiratory recordings during the following 2 h (recovery, 21% O2). Under these conditions, ventilatory LTF (gradual increase of minute ventilation during recovery) was clearly expressed in P10 rats but not in P1 and P4. In a second series of experiments, rat pups were exposed to CIH during the first 10 postnatal days (6 brief cyclic exposures at 5% O2 every 6 min followed by 1 h under normoxia, 24 h a day). Compared with P10 control rats, CIH enhanced hypoxic ventilatory response (estimated during the hypoxic cycles) specifically in male rat pups. Ventilatory LTF was drastically reduced in P10 rats exposed to CIH, which was associated with higher apnea frequency during recovery. We conclude that CIH from birth enhances hypoxic chemoreflex and disrupts LTF development, thus likely contributing to increase apnea frequency.

Intermittent hypoxia, a hallmark of sleep apnea, is a major factor for hypertension and impaired vasoreactivity.To examine the temporal occurrence of these two outcomes in order to provide insight into mechanisms and early cardiovascular disease identification.Functional and structural cardiovascular alterations were assessed in C57BL6 mice exposed to intermittent hypoxia (21-4% Fi(O(2)), 30-s cycle, 8 h/d) or air for up to 35 days. Blood pressure, heart rate, and urinary catecholamines were measured at Days 1 and 14. Hindquarter vasoreactivity was assessed at Days 14 and 35, including vasoconstriction to norepinephrine, endothelium-, and non-endothelium-dependent vasodilation. Aorta, heart, and hindquarter skeletal muscles were immunostained for vascular markers PECAM-1 and collagen IV.Hemodynamic alterations occurred from Day 1, characterized by blood pressure surges with bradytachyarrhythmia driven by cyclic hypoxia. At Day 14, blood pressure at normoxia was elevated, with predominant diastolic increase. With hypoxia, vasopressive catecholamines were elevated, blood pressure surged with a lower hypoxic threshold, whereas heart rate fluctuations decreased. Histologic alterations started from Day 14, with decreased endothelial PECAM-1 expression in descending aorta and left heart. Impaired peripheral vasoreactivity occurred at Day 35, including hypervasoconstriction to norepinephrine secondary to sympathetic hyperactivity, without changes in pre- and postsynaptic alpha-adrenoceptors or in endothelium- and non-endothelium-dependent vasodilation.Intermittent hypoxia induces sequential cardiovascular events suggesting increased chemoreflex and depressed baroreflex, resulting in sympathoadrenal hyperactivity, early hemodynamic alterations with proximal histologic remodeling, and delayed changes in peripheral vasoreactivity. Such early alterations before overt cardiovascular disease strengthen the need for identifying at-risk individuals for systematic treatment.

UNLABELLED Sustained hyperventilation has a time-limited effect on cerebrovascular dynamics. We investigated whether this effect was similar among brain regions by measuring regional cerebral blood volume (CBV) with steady-state susceptibility contrast magnetic resonance imaging during 3 h of hyperventilation. Regional CBV was determined in nine thiopental-anesthetized, mechanically-ventilated rats every 30 min in the dorsoparietal neocortex, the corpus striatum, and the cerebellum. The corpus striatum was the only brain region showing a stable reduction in CBV during the hypocapnic episode (PaCO(2), 24 +/- 3 mm Hg). In contrast, neocortex and, to a lesser extent, cerebellum exhibited a progressive return toward normal values despite continued hypocapnia. No evidence of a rebound in CBV was found on return to normal ventilation in the three brain regions. We conclude that sustained hyperventilation can lead to an uneven change in the reduction of CBV, possibly because of differences of brain vessels in their sensitivity to extracellular pH. Our results in neocortex confirm the transient effect of sustained hyperventilation on cerebral hemodynamics. IMPLICATIONS Sustained hyperventilation has a transient effect in decreasing cerebral blood volume (CBV). Using susceptibility contrast magnetic resonance imaging in thiopental-anesthetized rats, we found differences between brain regions in their transient CBV response to sustained hyperventilation.

Vessel size imaging is a new method that is based on simultaneous measurement of the changes Delta R(2) and Delta R(2)(*) in relaxation rate constants induced by the injection of an intravascular superparamagnetic contrast agent. Using the static dephasing approximation for Delta R(2)(*) estimation and the slow-diffusion approximation for Delta R(2) estimation, it is shown that the ratio Delta R(2)/Delta R(2)(*) can be expressed as a function of the susceptibility difference between vessels and brain tissue, the brain water diffusion coefficient, and a weighted mean of vessel sizes. Comparison of the results with 1) the Monte Carlo simulations used to quantify the relationship between tissue parameters and susceptibility contrast, 2) the experimental MRI data in the normal rat brain, and 3) the histologic data establishes the validity of this approach. This technique, which allows images of a weighted mean of the vessel size to be obtained, could be useful for in vivo studies of tumor vascularization. Magn Reson Med 45:397-408, 2001.

We used steady-state susceptibility contrast MRI to evaluate the regional cerebral blood volume (rCBV) response to hypocapnia in anesthetised rats. The rCBV was determined in the dorsoparietal neocortex, the corpus striatum, the cerebellum, as well as blood volume in extracerebral tissue (group 1). In addition, we used laser-Doppler flow (LDF) measurements in the left dorsoparietal neocortex (group 2), to correlate changes in CBV and in cerebral blood flow. Baseline values, expressed as a percentage of blood volume in each voxel, were higher in the brain regions than in extracerebral tissue. Hypocapnia (PaCO2 ≈ 25 mmHg) resulted in a significant decrease in CBV in the cerebellum (−17 ± 9%), in the corpus striatum (−15 ± 6%) and in the neocortex (−12 ± 7%), compared to the normocapnic CBV values (group 1). These changes were in good agreement with the values obtained using alternative techniques. No significant changes in blood volume were found in extracerebral tissue. The CBV changes were reversed during the recovery period. In the left dorsoparietal neocortex, the reduction in LDF (group 2) induced by hypocapnia (−21 ± 8%) was in accordance with the values predicted by the Poiseuille's law. We conclude that rCBV changes during CO2 manipulation can be accurately measured by susceptibility contrast MRI. Copyright ­© 2000 John Wiley & Sons, Ltd. Abbreviations used: ANOVA analysis of variancce CBF cerebral blood flow CBV cerebral blood volume CPMG Carr–Purcell–Meiboom–Gill FiO2 fractional inspired oxygen ICP intracranial pressure LDF laser-Doppler flow MABP mean arterial blood pressure MRI magnetic resonance imaging MTT mean transit time PaCO2 arterial partial pressure of carbon dioxide PaO2 arterial partial pressure of oxygen PET positron emission tomography rCBV regional cerebral blood volume SPECT single-photon emission computed tomography

Baroreflex is involved in the regulation of arterial blood pressure (BP). An increase in BP activates vagal inhibitory pathways to decrease heart rate; a concomitant decrease in sympathetic discharge reduces vascular resistance. Both responses reduce BP towards normal value. Conversely, a decrease in BP produces opposite effects to increase heart rate and vascular resistance.

We tested the hypothesis that exposure to neonatal intermittent hypoxia (n-IH) in rat pups alters central integrative processes following acute and intermittent peripheral chemoreceptor activation in adults. Newborn male rats were exposed to n-IH or normoxia for 10 consecutive days after birth. We then used both awake and anesthetized 3- to 4-mo-old rats to record ventilation, blood pressure, and phrenic and splanchnic nerve activities to assess responses to peripheral chemoreflex activation (acute hypoxic response) and long-term facilitation (LTF, long-term response after intermittent hypoxia). In anesthetized rats, phrenic and splanchnic nerve activities and hypoxic responses were also recorded with or without intact carotid body afferent signal (bilateral chemodenervation) or in response to electrical stimulations of the carotid sinus nerve. In awake rats, n-IH alters the respiratory pattern (higher frequency and lower tidal volume) and increased arterial blood pressure in normoxia, but the ventilatory response to repeated hypoxic cycles was not altered. In anesthetized rats, phrenic nerve responses to repeated hypoxic cycles or carotid sinus nerve stimulation were not altered by n-IH; however, the splanchnic nerve response was suppressed by n-IH compared with control. In control rats, respiratory LTF was apparent in anesthetized but not in awake animals. In n-IH rats, respiratory LTF was not apparent in awake and anesthetized animals. Following intermittent electrical stimulation, however, phrenic LTF was clearly present in n-IH rats, being similar in magnitude to controls. We conclude that, in adult n-IH rats: 1) arterial blood pressure is elevated, 2) peripheral chemoreceptor responses to hypoxia and its central integration are not altered, but splanchnic nerve response is suppressed, 3) LTF is suppressed, and 4) the mechanisms involved in the generation of LTF are still present but are masked most probably as the result of an augmented inhibitory response to hypoxia in the central nervous system.

International audience; We evaluated in vivo reflectance spectroscopy of visible light as a method to assess brain tissue hemoglobin oxygen saturation in rat striatum (SstrO2). Seven anesthetized and mechanically ventilated rats were subjected to incremental reduction in the fraction of inspired oxygen (Fio2): 0.35, 0.25, 0.15, 0.12, and 0.10, followed by a reoxygenation period (Group 1). At each episode, local changes in SstrO2 and in cerebral blood flow (LCBF) were simultaneously determined in the two striatal regions, using reflectance spectroscopy and laser Doppler flowmetry, respectively. Another group of rats (Group 2, n = 6) was also studied to measure sagittal sinus blood hemoglobin saturation (SssO2) during graded hypoxic hypoxia. Corpus striatum exhibited a significant graded decrease in SstrO2, from 38% +/- 17% at Fio2 of 0.35 (control) to 16% +/- 10% at Fio2 of 0.12 and to 13% +/- 7% at Fio2 of 0.10 (P < 0.05), with no difference between the two hemispheres. These local changes in SstrO2 were associated with a significant graded increase in LCBF: 161% +/- 26% of control values and 197% +/- 34% during these 2 hypoxic episodes, respectively (P < 0.05). All local changes were fully reversed during the reoxygenation period. In Group 2, SssO2 decreased from 38% +/- 8% at Fio2 of 0.35 (control) to 10% +/- 3% at Fio2 of 0.10, closely related to SstrO2 decreasing in hypoxia. This study shows that reflectance spectroscopy of the visible light in rat striatum could be a possible measure of continuous changes in SstrO2. SssO2 and LCBF measurements during graded hypoxic hypoxia indicate that changes in SstrO2 reflect primarily those in brain venous oxygenation.

Broad band light absorption spectroscopy in the visible range (520-590nm) has been carried out using implanted small optical fibers to probe the hemodynamics of deep tissues (striatum) in rat brain subjected to hypoxia. We observe a decrease of the cerebral blood oxygenation by a factor of up to two, while the cerebral blood volume (CBV) does not seem to increase significantly. However, nuclear magnetic resonance measurements of CBV in the same conditions using a magnetic contrast agent show that CBV increases by about 50%. This shows that absorption spectroscopy in the visible range strongly underestimates the CBV, probably due to the confinement of blood in vessels. This effect is confirmed by absorption spectroscopy measurements performed in phantoms with similar geometry.

Hyperpolarized 129Xe was dissolved in a lipid emulsion and administered to anaesthetized rats by manual injections into the carotid (approximately 1–1.5 mL in a maximum time of 30 s). During injection, 129Xe NMR brain spectra at 2.35 T were recorded over 51 s, with a repetition time of 253 ms. Two peaks assigned to dissolved 129Xe were observed (the larger at 194 ± 1 ppm assigned to intravascular xenon and the smaller at 199 ± 1 ppm to xenon dissolved in the brain tissue). Their kinetics revealed a rapid intensity increase, followed by a plateau (approximately 15 s duration) and then a decrease over 5 s. This behaviour was attributed to combined influences of the T1 relaxation of the tracer, of radiofrequency sampling, and of the tracer perfusion rate in rat brain. Similar kinetics were observed in experiments carried out on a simple micro-vessel phantom. An identical experimental set-up was used to acquire a series of 2D projection 129Xe images on the phantom and the rat brain.