Het gaat weer beter met de natuur in Nederland

In een Volkskrantinterview (22 mei 2009) poneerden de eerste drie auteurs de stelling, dat het weer beter gaat met de Nederlandse natuur. Aanleiding vormde de presentatie van de Monitor Duurzaam Nederland (CBS, 2009) waarbij het Planbureau concludeerde dat de biodiversiteit in ons land nog steeds achteruitholt. Dit artikel onderbouwt de stelling van 22 mei en is in feite een vervolg op een eerdere discussie, waarin de methodiek van het PBL werd gepresenteerd. Dit artikel gaat uit van de vraag hoe het gaat met de biodiversiteit en kijkt van daaruit naar de methode

Acute effects of insulin and insulin-induced hypoglycaemia on carotid body chemoreceptor activity and cardiorespiratory responses in dogs

Funding: Silvia V. Conde declares that Galvani Bioelectronics provided funds to support their work associated with Type 2 diabetic project.New Findings: What is the central question of this study? What are the effects of insulin and insulin-induced hypoglycaemia on carotid body chemoreceptor activity in vivo and how do carotid body chemoreceptor stimulation-mediated cardiorespiratory responses in beagle dogs compare during euglycaemia and insulin-induced hypoglycaemia? What is the main finding and its importance? Intracarotid insulin administration leads to sustained increase in carotid body chemoreceptor activity and respiratory response with significant cardiovascular effects. Insulin-induced hypoglycaemia exacerbated NaCN-mediated carotid body chemoreceptor activity and respiratory response with enhanced cardiovascular reflex response. These findings suggest that insulin-induced hypoglycaemia augments the carotid body chemoreceptors to initiate the adaptive counter-regulatory responses to restore the normoglycaemic condition. Abstract: The carotid body chemoreceptors (CBC) play an important role in the adaptive counter-regulatory response to hypoglycaemia by evoking the CBC-mediated sympathetic neuronal system to restore normoglycaemia. Ex vivo studies have shown varied responses of insulin-induced hypoglycaemia on CBC function, and several in vivo studies have indirectly established the role of CBCs in restoring normoglycaemia in both animals and humans. However, a direct effect of insulin and/or insulin-induced hypoglycaemia on CBC activity is not established in animal models. Therefore, the aim of this study was to evaluate in vivo effects of insulin and insulin-induced hypoglycaemia on CBC activity and cardiorespiration in a preclinical large animal model. The carotid sinus nerve (CSN) activity and cardiorespiratory responses to sodium cyanide (NaCN; 25 µg/kg) were compared before (euglycaemic) and after (hypoglycaemic) intracarotid administration of insulin (12.5–100 µU/dogs) in beagle dogs. Insulin administration increased CSN activity and minute ventilation ((Formula presented.) E) with significant (P < 0.0001) effects on heart rate and blood pressure. Insulin-mediated effects on CSN and cardiorespiration were sustained and the change in (Formula presented.) E was driven by tidal volume only. Insulin significantly (P < 0.0001) lowered blood glucose level. NaCN-mediated CSN activity and (Formula presented.) E were significantly (P < 0.0001) augmented during insulin-induced hypoglycaemia. The augmented (Formula presented.) E was primarily driven by respiratory frequency and partially by tidal volume. The cardiovascular reflex response mediated through CBC stimulation was significantly (P < 0.0001) exacerbated during insulin-induced hypoglycaemia. Collectively, these results demonstrate direct effects of insulin and insulin-induced hypoglycaemia on CBC chemosensitivity to potentiate CBC-mediated neuroregulatory pathways to initiate adaptive neuroendocrine and cardiorespiratory counter-regulatory responses to restore normoglycaemia.publishersversionepub_ahead_of_prin

d-Cystine di(m)ethyl ester reverses the deleterious effects of morphine on ventilation and arterial blood gas chemistry while promoting antinociception

We have identified thiolesters that reverse the negative effects of opioids on breathing without compromising antinociception. Here we report the effects of d-cystine diethyl ester (d-cystine diEE) or d-cystine dimethyl ester (d-cystine diME) on morphine-induced changes in ventilation, arterial-blood gas chemistry, A-a gradient (index of gas-exchange in the lungs) and antinociception in freely moving rats. Injection of morphine (10 mg/kg, IV) elicited negative effects on breathing (e.g., depression of tidal volume, minute ventilation, peak inspiratory flow, and inspiratory drive). Subsequent injection of d-cystine diEE (500 μmol/kg, IV) elicited an immediate and sustained reversal of these effects of morphine. Injection of morphine (10 mg/kg, IV) also elicited pronounced decreases in arterial blood pH, pO2 and sO2 accompanied by pronounced increases in pCO2 (all indicative of a decrease in ventilatory drive) and A-a gradient (mismatch in ventilation-perfusion in the lungs). These effects of morphine were reversed in an immediate and sustained fashion by d-cystine diME (500 μmol/kg, IV). Finally, the duration of morphine (5 and 10 mg/kg, IV) antinociception was augmented by d-cystine diEE. d-cystine diEE and d-cystine diME may be clinically useful agents that can effectively reverse the negative effects of morphine on breathing and gas-exchange in the lungs while promoting antinociception. Our study suggests that the d-cystine thiolesters are able to differentially modulate the intracellular signaling cascades that mediate morphine-induced ventilatory depression as opposed to those that mediate morphine-induced antinociception and sedation

Hypoxia releases S-nitrosocysteine from carotid body glomus cells—relevance to expression of the hypoxic ventilatory response

We have provided indirect pharmacological evidence that hypoxia may trigger release of the S-nitrosothiol, S-nitroso-L-cysteine (L-CSNO), from primary carotid body glomus cells (PGCs) of rats that then activates chemosensory afferents of the carotid sinus nerve to elicit the hypoxic ventilatory response (HVR). The objective of this study was to provide direct evidence, using our capacitive S-nitrosothiol sensor, that L-CSNO is stored and released from PGCs extracted from male Sprague Dawley rat carotid bodies, and thus further pharmacological evidence for the role of S-nitrosothiols in mediating the HVR. Key findings of this study were that 1) lysates of PGCs contained an S-nitrosothiol with physico-chemical properties similar to L-CSNO rather than S-nitroso-L-glutathione (L-GSNO), 2) exposure of PGCs to a hypoxic challenge caused a significant increase in S-nitrosothiol concentrations in the perfusate to levels approaching 100 fM via mechanisms that required extracellular Ca2+, 3) the dose-dependent increases in minute ventilation elicited by arterial injections of L-CSNO and L-GSNO were likely due to activation of small diameter unmyelinated C-fiber carotid body chemoafferents, 4) L-CSNO, but not L-GSNO, responses were markedly reduced in rats receiving continuous infusion (10 μmol/kg/min, IV) of both S-methyl-L-cysteine (L-SMC) and S-ethyl-L-cysteine (L-SEC), 5) ventilatory responses to hypoxic gas challenge (10% O2, 90% N2) were also due to the activation of small diameter unmyelinated C-fiber carotid body chemoafferents, and 6) the HVR was markedly diminished in rats receiving L-SMC plus L-SEC. This data provides evidence that rat PGCs synthesize an S-nitrosothiol with similar properties to L-CSNO that is released in an extracellular Ca2+-dependent manner by hypoxia

L-cysteine ethyl ester prevents and reverses acquired physical dependence on morphine in male Sprague Dawley rats

The molecular mechanisms underlying the acquisition of addiction/dependence on morphine may result from the ability of the opioid to diminish the transport of L-cysteine into neurons via inhibition of excitatory amino acid transporter 3 (EAA3). The objective of this study was to determine whether the co-administration of the cell-penetrant L-thiol ester, L-cysteine ethyl ester (L-CYSee), would reduce physical dependence on morphine in male Sprague Dawley rats. Injection of the opioid-receptor antagonist, naloxone HCl (NLX; 1.5 mg/kg, IP), elicited pronounced withdrawal phenomena in rats which received a subcutaneous depot of morphine (150 mg/kg) for 36 h and were receiving a continuous infusion of saline (20 μL/h, IV) via osmotic minipumps for the same 36 h period. The withdrawal phenomena included wet-dog shakes, jumping, rearing, fore-paw licking, 360° circling, writhing, apneas, cardiovascular (pressor and tachycardia) responses, hypothermia, and body weight loss. NLX elicited substantially reduced withdrawal syndrome in rats that received an infusion of L-CYSee (20.8 μmol/kg/h, IV) for 36 h. NLX precipitated a marked withdrawal syndrome in rats that had received subcutaneous depots of morphine (150 mg/kg) for 48 h) and a co-infusion of vehicle. However, the NLX-precipitated withdrawal signs were markedly reduced in morphine (150 mg/kg for 48 h)-treated rats that began receiving an infusion of L-CYSee (20.8 μmol/kg/h, IV) at 36 h. In similar studies to those described previously, neither L-cysteine nor L-serine ethyl ester (both at 20.8 μmol/kg/h, IV) mimicked the effects of L-CYSee. This study demonstrates that 1) L-CYSee attenuates the development of physical dependence on morphine in male rats and 2) prior administration of L-CYSee reverses morphine dependence, most likely by intracellular actions within the brain. The lack of the effect of L-serine ethyl ester (oxygen atom instead of sulfur atom) strongly implicates thiol biochemistry in the efficacy of L-CYSee. Accordingly, L-CYSee and analogs may be a novel class of therapeutics that ameliorate the development of physical dependence on opioids in humans

Ventilatory Chemosensory Drive Is Blunted in the <i>mdx</i> Mouse Model of Duchenne Muscular Dystrophy (DMD)

<div><p>Duchenne Muscular Dystrophy (DMD) is caused by mutations in the DMD gene resulting in an absence of dystrophin in neurons and muscle. Respiratory failure is the most common cause of mortality and previous studies have largely concentrated on diaphragmatic muscle necrosis and respiratory failure component. Here, we investigated the integrity of respiratory control mechanisms in the <i>mdx</i> mouse model of DMD. Whole body plethysmograph in parallel with phrenic nerve activity recordings revealed a lower respiratory rate and minute ventilation during normoxia and a blunting of the hypoxic ventilatory reflex in response to mild levels of hypoxia together with a poor performance on a hypoxic stress test in <i>mdx</i> mice. Arterial blood gas analysis revealed low PaO₂ and pH and high PaCO₂ in <i>mdx</i> mice. To investigate chemosensory respiratory drive, we analyzed the carotid body by molecular and functional means. Dystrophin mRNA and protein was expressed in normal mice carotid bodies however, they are absent in <i>mdx</i> mice. Functional analysis revealed abnormalities in Dejours test and the early component of the hypercapnic ventilatory reflex in <i>mdx</i> mice. Together, these results demonstrate a malfunction in the peripheral chemosensory drive that would be predicted to contribute to the respiratory failure in <i>mdx</i> mice. These data suggest that investigating and monitoring peripheral chemosensory drive function may be useful for improving the management of DMD patients with respiratory failure.</p></div

Reduced peripheral chemosensory drive in anesthetized <i>mdx</i> mice.

<p>A) The Dejours test adapted to small rodents was utilized and the first 10 s of hyperoxia exposure were analyzed. The peripheral chemosensory drive was significantly affected in <i>mdx</i> mice compared to normal mice. B) The first 10 s of exposure to air-balanced hypercapnia or O₂-balanced hypercapnia were analyzed as the fast component of the HCVR. The HCVR induced by air-balanced hypercapnic gas mix (empty bar) was attenuated in normal mice compared to the HCVR induced by the hyperoxia-balanced hypercapnia mix (hatched bar). In the <i>mdx</i> mice, the early HCVR induced by air-balanced hypercapnic gas mix (gray bar) was similar to the early HCVR induced by the hyperoxia-balanced hypercapnia gas mix (filled bar). The analysis also showed a significant attenuation of the fast component of the HCVR in <i>mdx</i> mice compared to normal mice exposed to either air-balanced or hyperoxia-balanced hypercapnic gas mixtures. Mean ± SEM; * p<0.05, *** p<0.001. n = 4.</p

HVR of normal and <i>mdx</i> mice exposed to different FiO₂ levels.

<p>A) Representative inspiratory and expiratory flows obtained from normal (top) and <i>mdx</i> mice (bottom) exposed to FiO₂ 21, 18, 15, 12, 10, 8 and 100%. Each animal was challenged three times with each FiO₂. The scale for tidal volume (V_T, µL) and time (s) are shown at bottom right. B) Quantification of respiratory frequency (<i>f</i>_R, Hz), C) tidal volume normalized by body weight (µL/g) and D) minute ventilation () normalized by body weight (µL/s/g) from normal (empty bars) and <i>mdx</i> (filled bars) mice at each FiO₂ levels tested. Mean ± SEM; * p<0.05; ** p<0.01, n = 5.</p

Expression of dystrophin in the CB from normal and <i>mdx</i> mice.

<p>A) Dystrophin mRNA expression level in the CB from normal mice is similar to that in <i>tibialis anterior</i>, whereas dystrophin mRNA was not detected in the two tissues from <i>mdx</i> mice. The delta Ct values obtained were TA 18. 85±0.31 and CB 25.51±0.07 (mean ± SD). Dystrophic TA and CB amplification were under the minimum level of detection, being considered as undetermined. B) Immunoblot showing expression of full length dystrophin protein in CB from normal mice and absence in CB from <i>mdx</i> mice.</p