Anders Forslid

Endothelial Dysfunction After Repeated Chlamydia pneumoniae Infection in Apolipoprotein E–Knockout Mice

BackgroundArterial relaxation is largely regulated by endothelial nitric oxide (NO). Its diminished activity has been associated with incipient atherosclerosis. We investigated the endothelium-dependent relaxation of aorta in apolipoprotein E–knockout (apoE-KO) mice exposed to single or repeated Chlamydia pneumoniae inoculation. Methods and ResultsForty-eight apoE-KO mice, 8 weeks old, were inoculated intranasally with C pneumoniae (n=24) or saline (n=24) every 2 weeks over a 6-week period. Twenty mice (10 infected and 10 controls) were killed at 2 weeks and 6 weeks, respectively, after the first inoculation. The smooth muscle tone of aortic rings was measured in vitro at both time points. The norepinephrine-precontracted thoracic aortic rings were successively exposed to methacholine in the absence and presence of NG-nitro-l-arginine methyl ester (L-NAME) and diclofenac. The methacholine-induced relaxation was attenuated in the infected mice at 6 weeks in both the absence and presence of L-NAME (P <0.05 and P <0.01, respectively). When administered together with L-NAME, diclofenac enhanced the relaxation of the L-NAME–pretreated aortas in infected mice at 2 weeks (P <0.05) but not in noninfected mice. The relaxation response from infected mice tended to differ in the same manner at 6 weeks (P <0.1). No intimal thickening was detected at either time point. ConclusionsC pneumoniae impairs arterial endothelial function, and the NO pathway is principally involved. Cyclooxygenase-dependent vasoconstricting products may also account for the infection-induced impaired relaxation. These findings further support the role of C pneumoniae infection in atherosclerosis development.

The effect of high post-mortem temperature on the development of pale, soft and exudative pork: Interaction with ultimate pH

The effects of post-mortem temperature and ultimate pH (pH(u), 24 h post mortem) on the development of the pale, soft and exudative (PSE) characteristics in pig longissimus dorsi muscle were studied. Ten out of the 13 pigs used received pre-slaughter injections of adrenaline in order to deplete muscle glycogen stores. The two muscles from each pig were held at 12 or 35°C during rigor mortis development. Results from covariance analysis, using pH(u) as covariate, showed that a high temperature (35°C) resulted in a dramatic increase in internal light scattering (FOP) 24 h post mortem and a significant decrease in water- and salt-soluble proteins. Cooking loss, sarcomere length and drip loss did not vary significantly with rigor temperature. Interaction between temperature and pH(u) was estimated by assessing the relationship between pH(u) and the difference between the two rigor temperatures for selected traits. The best predictive model was a segmented quadratic model with a plateau which gave significant results for FOP, drip loss, water- and salt-soluble proteins. The effect of temperature decreased curvilinearly when pH increased until a constant value above which no noticeable difference was recorded (drip loss, water- and salt-soluble proteins) or a constant difference was reached (FOP). The pH values corresponding to the convergence points differed from one trait to another. They ranged from 5·72 to 6·22. These results illustrate the importance of muscle glycogen content at slaughter and subsequent pH(u) with regard to the development of temperature-induced PSE meat.

Acute Chlamydia pneumoniae infection causes coronary endothelial dysfunction in pigs.

BACKGROUND Coronary endothelial dysfunction contributes to the pathogenesis of acute coronary syndromes (ACSs). Acute Chlamydia pneumoniae infection has been epidemiologically associated with ACS. In this study, we investigated whether acute C. pneumoniae infection could alter the endothelial vasomotor function of porcine coronary vessels. METHODS AND RESULTS Twenty pigs, 7-9 kg in weight, were inoculated intratracheally with C. pneumoniae (n=12) or saline (n=8), and investigated at 3 days (five infected/four non-infected) and 2 weeks (5+2 infected/four non-infected) after inoculation. The endothelium-dependent reactivity of coronary microcirculation was assessed at both time points by measuring peak coronary flow velocity (CFV) in response to bradykinin, before and after infusions with glutathione, an antioxidant, and L-arginine, a substrate for nitric oxide synthase (NOS). CFV after bradykinin was significantly decreased in infected animals at both time points. At 2 weeks, both glutathione and L-arginine significantly improved CFV after bradykinin. CFV after sodium nitroprusside (SNP) was similar in both groups. At 3 days, the relaxation responses of bradykinin-induced pre-contracted left anterior descending (LAD) coronary rings to bradykinin were significantly less in infected animals. N(G)-nitro-L-arginine-methyl-ester, an NOS inhibitor, had significantly greater inhibitory effect on bradykinin-induced relaxation in infected animals. Plasma nitrate-nitrite and fibrinogen, and NOS activity from LAD coronary samples were significantly increased in infected animals. CONCLUSION Acute C. pneumoniae infection causes endothelial dysfunction of both resistance and epicardial coronary vessels, and favours a pro-coagulant status. These effects could in part account for the epidemiologically suggested association between acute infection and ACS.

Effects of CO2 anaesthesia on central nervous system activity in swine

The objective of the study was to examine the changes in central nervous system (CNS) activity and physical behaviour during induction and awakening from CO2 anaesthesia. Two studies, each using pigs immersed into 90% CO2 gas for a period of 60 s were performed. In study 1, we monitored middle latency auditory evoked potentials (changes in latencies, amplitudes and a depth of anaesthesia index), electroencephalographic parameters (delta, theta, alpha and beta electroencephalographic power and 95% spectral edge frequency) and heart rate; and in study 2, we monitored body movements and arterial and venous partial pressure of CO2 and O2. No behavioural signs of distress were observed during the early part of the induction. The swine exhibited muscular activity from 13-30 s after induction-start as well as during awakening from anaesthesia, possibly because of a transitory weaker suppression of the brain stem than of the cortex. The CNS and blood gas parameters started to change from the very start of induction. The CNS suppression lasted only approximately one minute after the end of the induction period. The two studies indicated a good temporal relationship between changes in amplitude, depth of anaesthesia index, spectral edge frequency, and arterial P CO2 during the induction period.

Co-Infection with CHLAMYDIA PNEUMONIAE and HELICOBACTER PYLORI Results in Vascular Endothelial Dysfunction and Enhanced VCAM-1 Expression in ApoE-Knockout Mice.

Background: Upregulation of proinflammatory endothelial cell adhesion molecules and decreased bioactivity of endothelial nitric oxide (NO) are important in the pathogenesis of atherosclerosis. We investigated the effects of co-infection with Chlamydia pneumoniae and Helicobacter pylori on these two events in apoE-KO mice. Methods: Thirty-two apoE-KO mice, 8 weeks old, were equally divided into 4 groups. The first 2 groups were infected with either C. pneumoniae or H. pylori, while the 3rd group was infected with both C. pneumoniae and H. pylori. Mice from the 4th group and 4 wild-type mice served as controls. Thoracic and abdominal aortas were harvested after 10 weeks, and staining for vascular cell adhesion molecule-1 (VCAM-1) and intracellular adhesion molecule-1 was analyzed by immunocytochemistry. The endothelial vasomotor responses of thoracic aortas to methacholine were studied in organ chambers in the absence and presence of L-NAME. The plasma levels of nitrate/nitrite were measured. Results: Staining for VCAM-1 was more intense at the branching sites of aortas from mice with co-infection than in mono-infected or noninfected apoE-KO mice. The relaxation responses to methacholine and the plasma levels of nitrate/nitrite were significantly less in the co-infected group than in the other groups (p < 0.05). Conclusion: Co-infection of apoE-KO mice with C. pneumoniae and H. pylori seems to be associated with impaired bioactivity of endothelial NO and increased expression of VCAM-1 at branching sites. The findings may suggest an additive interaction of these pathogens in atherogenesis.

CO2 induced acute respiratory acidosis and brain tissue intracellular pH: a 31P NMR study in swine

High concentration carbon dioxide (CO2) is used to promote pre-slaughter anaesthesia in swine and poultry, as well as short-lasting surgical anaesthesia and euthanasia in laboratory animals. Questions related to animal welfare have been raised, as CO2 anaesthesia does not set in momentarily. Carbon dioxide promotes anaesthesia by lowering the intracellular pH in the brain cells, but the dynamics of the changes in response to a high concentration of CO2 is not known. Based on 31P NMR spectroscopy, we describe CO2-induced changes in intracellular pH in the brains of five pigs inhaling 90% CO2 in ambient air for a period of 60 s, and compare the results to changes in arterial blood pH, PCO2, O2 saturation and HCO3 - concentration. The intracellular pH paralleled the arterial pH and PCO2 during inhalation of CO2; and it is suggested that the acute reaction to CO2 inhalation mainly reflects respiratory acidosis, and not metabolic regulation as for example transmembrane fluxes of H+/HCO3 -. The intracellular pH decreased to approximately 6.7 within the 60 s inhalation period, and the situation was metabolically reversible after the end of CO2 inhalation. The fast decrease in intracellular pH supports the conclusion that high concentration CO2 leads to anaesthesia soon after the start of inhalation.

Middle-latency auditory evoked potentials during induction of thiopentone anaesthesia in pigs.

A method is described for measuring middle-latency auditory evoked potentials (MLAEP) in consciously awake, non-sedated pigs during the induction of thiopentone anaesthesia (0.6 ml/kg, 2.5% thiopentone solution). It was done by using autoregressive modelling with an exogenous input (ARX). The ability to perceive pain during the induction was compared with (1) the changes in latencies and amplitudes of the MLAEP, (2) the change in a depth of anaesthesia index based on the ARX-model and (3) the change in the 95% spectral edge frequency. The pre-induction MLAEP was easily recordable and looked much like the one in man, dogs and rats. The temporal resolution in the ARX method was sufficiently high to describe the fast changes occurring during induction of thiopentone anaesthesia. As previously reported from studies in man, dogs and rats, induction of thiopentone anaesthesia resulted in significantly increased latencies and decreased amplitudes of the MLAEP trace as well as in a significantly reduced depth of anaesthesia index and spectral edge frequency. None of the changes, however, related well to the ability to react to a painful stimulus. Whether an ARX-based depth of anaesthesia index designed especially for pigs might be better than the present index (designed for man) for assessing depth of anaesthesia must await the results of further studies.

Effect of time between adrenaline injection and slaughter on the rate and extent of post-mortem metabolism in porcine skeletal muscle

The aim of this work was to study the effect of time between adrenaline injection and slaughter on the rate and extent of post-mortem metabolism in pig muscle. Five pigs were subcutaneously injected with adrenaline (0·3 mg/kg) or with a saline solution 4 h, 1 h or 15 min prior to slaughter. pH(1), pH(u) and FOP(u) were measured in Longissimus dorsi (LD) and Biceps femoris (BF) muscles. m.LD samples were taken 20 days before slaughter using biopsy sampling, immediately after bleeding and 45 min post mortem for biochemical analysis. m.LD glycolytic potential (very close to glycogen content) was decreased by the injection of adrenaline 4 h and 1 h prior to slaughter, when comparing values at rest (20 days before slaughter) and values determined immediately after bleeding. The depletion was greater fro the injection performed 4 h before slaughter. In this group pH(u) was higher foe adrenaline-injected pigs (5·69 versus 5·47 for pigs injected with saline solution) but the difference was not significant. Pigs injected with adrenaline 1 h prior to slaughter exhibited higher glucose, glucose-6-phosphate and lactate levels immediately after slaughter, lower pH(1) and higher FOP values in m.LD than control pigs. Since the differences in pH(1) were not explained by differences in the rate of build-up of lactate, it was hypothesized that pigs injected with adrenaline 1 h prior to slaughter had lower muscle pH at slaughter. It was concluded that the rate or the extent of post mortem metabolism in pig muscle may be affected independently, by manipulating the time between adrenaline injection and slaughter.

Coronary flow and reactivity, but not arrhythmia vulnerability, are affected by cardioplegia during cardiopulmonary bypass in piglets

BackgroundSurgery under cardiopulmonary bypass (CPB) is still associated with significant cardiovascular morbidity in both pediatric and adult patients but the mechanisms are not fully understood. Abnormalities in coronary flow and function have been suggested to play an important role. Prior studies suggest protective effects on coronary and myocardial function by short intravenous (i.v.) infusion of cyclosporine A before CPB.MethodsBarrier-bred piglets (10–12 kg, n=20) underwent CPB for 45 min, with or without antegrade administration of cardioplegic solution. Prior to CPB, half of the animals in each group received an i.v. infusion of 100 mg/kg cyclosporine A. The left anterior descending coronary flow velocity responses to adenosine, serotonin, and atrial pacing, as well as left ventricular function and postsurgical vulnerability to atrial fibrillation (Afib) were assessed by intracoronary Doppler, epicardial echocardiography, and in vivo electrophysiological study, before and 8 hours after surgery. Plasma C-reactive protein (CRP) and fibrinogen were measured at both time-points.ResultsCyclosporine infusion did not influence any of the studied variables (p>0.4). Coronary peak flow velocity (cPFV) rose significantly after surgery especially in the cardioplegia group (p<0.01 vs. non-cardioplegia group and pre-surgery). cPFV responses to adenosine, but not to serotonin, tended to decrease (p=0.06) after surgery only in cardioplegia group (p=0.06; p=0.8 in non-cardioplegia group vs pre-surgery). Also, cPFV response to atrial pacing was lower in the cardioplegia than in the non-cardioplegia group (p=0.02). Neither vulnerability nor duration of induced Afib after CPB differed between groups (Chi-square p=0.4). Cyclosporine had no significant effect on coronary indexes or arrhythmia vulnerability (p>0.4). There was no difference in systolic myocardial function between groups at any time point.ConclusionIn piglets, CPB with cardioplegia was associated with profound abnormalities in coronary vasomotor tone and receptor-related flow regulation, whereas arrhythmia vulnerability appeared to be comparable with that in non-cardioplegia group. In this study, preconditioning with cyclosporine had no detectable protective effect on coronary circulation or arrhythmia vulnerability after CPB.

Coronary flow and reactivity, but not arrhythmia vulnerability, are affected by cardioplegia during cardiopulmonary bypass surgery of piglets

Introduction: Cardiopulmonary bypass (CPB) surgery remains associated with significant cardiovascular morbidity in both pediatric and adult patients but the mechanisms are not fully clarified. Abnormalities in coronary flow and function have beensuggested to play an important role. A few prior studies suggested protective effects on coronary and myocardial function by short intravenous (i.v.) infusion of cyclosporine A prior to CPB surgery. Methods: Barrier-bred piglets (10-12 kg, n=20) were subjected to CPB with (n=10) or without (n=10) antegrade administration for 20 minutes of cardioplegic solution. Prior to surgery, half of animals from each group received 10-minute i.v. infusion of 100 mg/kg cyclosporine A. Left anterior descending coronary flow velocity responses to adenosine, serotonin, and atrial pacing, as well as left ventricular function and postsurgical vulnerability to atrial fibrillation (Afib) were assessed by intracoronary Doppler, epicardial echocardiography, and in vivo electrophysiological study, respectively. Results: Coronary peak flow velocity (cPFV) rose significantly after surgery, especially in cardioplegia group (p0.4). There was no difference in systolic myocardial function between groups at any timepoint. Conclusions: Cardioplegia during CPB surgery of piglets was associated with profound abnormalities in coronary vasomotor tone and receptor-related flow regulation, whereas arrhythmia vulnerability appeared to be comparable with that in non-cardioplegia group. In this study, intracoronary pretreatment with cyclosporine had no observable protective effect on coronary circulation or arrhythmia vulnerability after CPB surgery.