Impact of anesthesia on cardiac function during echocardiography in mice

Anesthetics provide sedation and immobility facilitating echocardiography in mice, but influence cardiac function. We studied the effects of intraperitoneal and inhaled anesthetic agents on echocardiographic measurements. Mice were anesthetized with intraperitoneal tribromoethanol (TBE), ketamine-midazolam (K/M), ketamine-xylazine (K/X), or inhaled isoflurane (Isf), and echocardiographic parameters were assessed at 5, 10, 15, and 20 min. In C57BL/6N mice, Isf produced high initial heart rates (HR) that decreased to levels comparable to TBE at 15-20 min (approximately 450 beats/min) and the most stable percent fractional shortening (%FS) and end-diastolic dimension (EDD). With TBE, %FS initially was low, but increased comparable to Isf (approximately 45%) at 15 min. K/M produced similar time trends but lower absolute values compared with TBE for all parameters. K/X produced cardiac depression evidenced by low HR and %FS, and increased EDD. Isf was the most reproducible in repeat studies at 12 days. In C57BL/6J compared with C57BL/6N mice, K/M produced higher HR, and %FS and TBE produced smaller EDD. In conclusion, anesthetic agent, timing of echocardiographic measurements, and genetic background are all critical variables during echocardiography in mice.     

Effects of CMYA1 overexpression on cardiac structure and function in mice

CMYA1(cardiomyopathy-associated protein 1,also termed Xin)localizes to the intercalated disks(ICDs)of the myocardium and functions to maintain ICD structural in...     

Ischemia-reperfusion injury leads to distinct temporal cardiac remodeling in normal versus diabetic mice

Diabetes is associated with higher incidence of myocardial infarction (MI) and increased propensity for subsequent events post-MI. Here we conducted a temporal analysis of the influence of diabetes on cardiac dysfunction and remodeling after ischemia reperfusion (IR) injury in mice. Diabetes was induced using streptozotocin and IR performed by ligating the left anterior descending coronary artery for 30 min followed by reperfusion for up to 42 days. We first evaluated changes in cardiac function using echocardiography after 24 hours reperfusion and observed IR injury significantly decreased the systolic function, such as ejection fraction, fractional shortening and end systolic left ventricular volume (LVESV) in both control and diabetic mice. The longitudinal systolic and diastolic strain rate were altered after IR, but there were no significant differences between diabetic mice and controls. However, a reduced ability to metabolize glucose was observed in the diabetic animals as determined by PET-CT scanning using 2-deoxy-2-((18)F)fluoro-D-glucose. Interestingly, after 24 hours reperfusion diabetic mice showed a reduced infarct size and less apoptosis indicated by TUNEL analysis in heart sections. This may be explained by increased levels of autophagy detected in diabetic mice hearts. Similar increases in IR-induced macrophage infiltration detected by CD68 staining indicated no change in inflammation between control and diabetic mice. Over time, control mice subjected to IR developed mild left ventricular dilation whereas diabetic mice exhibited a decrease in both end diastolic left ventricular volume and LVESV with a decreased intraventricular space and thicker left ventricular wall, indicating concentric hypertrophy. This was associated with marked increases in fibrosis, indicted by Masson trichrome staining, of heart sections in diabetic IR group. In summary, we demonstrate that diabetes principally influences distinct IR-induced chronic changes in cardiac function and remodeling, while a smaller infarct size and elevated levels of autophagy with similar cardiac function are observed in acute phase.     

Met signaling in cardiomyocytes is required for normal cardiac function in adult mice

Hepatocyte growth factor (HGF) and its receptor, Met, are key determinants of distinct developmental processes. Although HGF exerts cardio-protective effects in a number of cardiac pathologies, it remains unknown whether HGF/Met signaling is essential for myocardial development and/or physiological function in adulthood. We therefore investigated the requirement of HGF/Met signaling in cardiomyocyte for embryonic and postnatal heart development and function by conditional inactivation of the Met receptor in cardiomyocytes using the Cre-α-MHC mouse line (referred to as α-MHCMet-KO). Although α-MHCMet-KO mice showed normal heart development and were viable and fertile, by 6 months of age, males developed cardiomyocyte hypertrophy, associated with interstitial fibrosis. A significant upregulation in markers of myocardial damage, such as β-MHC and ANF, was also observed. By the age of 9 months, α-MHCMet-KO males displayed systolic cardiac dysfunction. Mechanistically, we provide evidence of a severe imbalance in the antioxidant defenses in α-MHCMet-KO hearts involving a reduced expression and activity of catalase and superoxide dismutase, with consequent reactive oxygen species accumulation. Similar anomalies were observed in females, although with a slower kinetics. We also found that Met signaling down-regulation leads to an increase in TGF-β production and a decrease in p38MAPK activation, which may contribute to phenotypic alterations displayed in α-MHCMet-KO mice. Consistently, we show that HGF acts through p38α to upregulate antioxidant enzymes in cardiomyocytes. Our results highlight that HGF/Met signaling in cardiomyocytes plays a physiological cardio-protective role in adult mice by acting as an endogenous regulator of heart function through oxidative stress control.     

Comparison of xylazine with tiletamine-zolazepam (Telazol) and xylazine-ketamine anesthesia in rabbits

Although widely used to provide short term anesthesia, ketamine-xylazine does not always produce satisfactory anesthesia. We compared the efficacy of ketamine-xylazine to tiletamine-zolazepam-xylazine for producing surgical anesthesia in rabbits. Four of six rabbits receiving ketamine-xylazine and all of the 12 animals given tiletamine-zolazepam-xylazine were anesthetized successfully. The mean surgical anesthesia time in the ketamine-xylazine group was 35 +/- 6 minutes as compared to the tiletamine-zolazepam-xylazine group, 72 +/- 8 minutes (p less than 0.05). There was no significant difference in the interval between the injection of the different anesthetic mixtures and the loss of either the righting reflex, the jaw reflex or the toe web pinch reflex. Respiratory rates and arterial oxygen partial pressure were higher in the ketamine-xylazine group (p less than 0.05). However, in both groups arterial blood pressure and arterial PO2 were lowered, while arterial PCO2 was elevated. No nephrotoxicity occurred. Tiletamine-zolazepam-xylazine provides effective surgical anesthesia in rabbits and in many cases may be preferable to conventional ketamine-xylazine regimen.     

Sarcospan-deficient mice maintain normal muscle function

Sarcospan is an integral membrane component of the dystrophin-glycoprotein complex (DGC) found at the sarcolemma of striated and smooth muscle. The DGC plays important roles in muscle function and viability as evidenced by defects in components of the DGC, which cause muscular dystrophy. Sarcospan is unique among the components of the complex in that it contains four transmembrane domains with intracellular N- and C-terminal domains and is a member of the tetraspan superfamily of proteins. Sarcospan is tightly linked to the sarcoglycans, and together these proteins form a subcomplex within the DGC. Stable expression of sarcospan at the sarcolemma is dependent upon expression of the sarcoglycans. Here we describe the generation and analysis of mice carrying a null mutation in the Sspn gene. Surprisingly, the Sspn-deficient muscle maintains expression of other components of the DGC at the sarcolemma, and no gross histological abnormalities of muscle from the mice are observed. The Sspn-deficient muscle maintains sarcolemmal integrity as determined by serum creatine kinase and Evans blue uptake assays, and the Sspn-deficient muscle maintains normal force and power generation capabilities. These data suggest either that sarcospan is not required for normal DGC function or that the Sspn-deficient muscle is compensating for the absence of sarcospan, perhaps by utilizing another protein to carry out its function.     

Cardiorespiratory effects of diazepam-ketamine, xylazine-ketamine and thiopentone anesthesia in male Wistar rats--a comparative analysis

Several anesthetics are known to cause respiratory and cardiovascular depression in humans and animals; but, these diverse effects have not been extensively investigated in laboratory rodents. The objective of this study is to choose a suitable anesthetic combination for use in surgical models eg. coronary artery ligation in rats. Male Wistar rats were anesthetized with three different drugs viz. diazepam-ketamine (DK) (2.5 mg/Kg, intraperitoneally (i.p); 50 mg/Kg, i.p), xylazine-ketamine (XK) (5 mg/Kg i.p; 50 mg/Kg i.p) and thiopentone (T) (40 mg/Kg i.p) and the respiratory and cardiovascular functions were assessed after coronary artery ligation. Heart rate (HR), mean arterial pressure (MAP), partial pressure of carbon dioxide (PaCO2), partial pressure of oxygen (PaO2), oxygen saturation percentage (O2 sat (%)), arterial blood pH and rectal body temperature were studied in detail. During the anesthetic regime, HR was lower till 60 min in XK and T ligated group (333 +/- 6; 304 +/- 8 beats/min) and it was near normalcy in the case of DK ligated group (394 +/- 6 beats/min). Significant respiratory depression was particularly reflected in the T ligated group with an increase in PaCO2 at 30 min (40.32 +/- 2.64 mmHg), which decreased to 38.2 +/- 2.23 mmHg at 60 min. Throughout the investigation, DK showed the least overall effects compared to XK and T on respiratory functions. Thus, DK could be considered to be a suitable anesthetic for use in a surgical model such as coronary artery ligation in albino rats.     

Effects of cardiac denervation on its function in asphyxia]

It has been established in 23 experiments on dogs that during asphyxia the reactions of denervated heart which were directed toward compensation of hypoxia in the whole organism and towards preservation of myocardium from hypoxia damages were slower than that in the norm. All these processes led to the overloading of myocardium.     

Pro-apoptotic versus anti-apoptotic properties of dietary resveratrol on tumoral and normal cardiac cells

Resveratrol is a natural dietary polyphenol found in grape skin, red wine, and various other food products. Resveratrol has proved to be an effective chemopreventive agent for different malignant tumors. It has also been shown to prevent vascular alterations such as atherosclerosis and inflammatory-associated events. In view of these observations, we investigated the anti-proliferative and pro-apoptotic activities of resveratrol on a tumoral cardiac cell line (HL-1 NB) derived from mouse tumoral atrial cardiac myocytes. These effects were compared with those found on normal neonatal mouse cardiomyocytes. HL-1 NB cells and neonatal cardiomyocytes were treated with resveratrol (5, 30, and/or 100 μM) for different times of culture (24, 48, and/or 72 h). Resveratrol effects were determined by various microscopical and flow cytometric methods. After resveratrol treatment, a strong inhibition of tumoral cardiac HL1-NB cell growth associated with a loss of cell adhesion was observed. This cell proliferation arrest was associated with an apoptotic process revealed by an increased percentage of cells with fragmented and/or condensed nuclei (characteristic of apoptotic cells) identified after staining with Hoechst 33342 and by the presence of cells in subG1. At the opposite, on normal cardiomyocytes, no cytotoxic effects of resveratrol were observed, and a protective effect of resveratrol against norepinephrine-induced apoptosis was found on normal cardiomyocytes. Altogether, the present data demonstrate that resveratrol (1) induces apoptosis of tumoral cardiac HL1-NB cells, (2) does not induce cell death on normal cardiomyocytes, and (3) prevents norepinephrine-induced apoptosis on normal cardiomyocytes.     

Influence of tail versus cardiac sampling on blood glucose and lipid profiles in mice

Blood is collected during animal experimentation to measure haematological and metabolic parameters. It cannot be assumed that circulating blood has the same composition irrespective of its location, and indeed, differences in the composition of blood sampled from the arterial and venous compartments have been reported. Here we investigated whether blood collected by cardiac puncture (CP) versus that collected following removal of the distal 1 mm of the tail tip (TT) differs with respect to glucose and lipid profiles in male C57BL/6J mice at 4, 7, 20 and 28 weeks of age. Blood was first collected from the TT of unanaesthetized mice, which were then immediately anaesthetized using ketamine/xylazine, and a second blood sample was collected by CP. The CP glucose concentration was significantly higher than TT glucose by a positive bias averaging +80% (P < 0.01), irrespective of the age of the mice. Conversely, the concentrations of the CP lipids, including total cholesterol, high-density lipoprotein cholesterol and triglyceride were lower than TT lipids by a negative bias averaging -25% (P < 0.05). These observations highlight the difficulty in measuring and comparing metabolic parameters such as glucose and lipid between one blood compartment and another. They illustrate the need to standardize sampling sites, especially when repeated blood sampling is required.     

Lack of osteopontin improves cardiac function in streptozotocin-induced diabetic mice

The purpose of this study was to investigate the role of osteopontin (OPN) in diabetic hearts. Diabetes was induced in wild-type (WT) and OPN knockout (KO) mice by using streptozotocin (150 mg/kg) injection. Left ventricular (LV) structural and functional remodeling was studied 30 and 60 days after induction of diabetes. Induction of diabetes increased OPN expression in cardiac myocytes. Heart weight-to-body weight ratio was increased in both diabetic (D) groups. Lung wet weight-to-dry weight ratio was increased only in the WT-D group. Peak left ventricular (LV) developed pressures measured using Langendorff perfusion analyses were reduced to a greater extent in WT-D versus KO-D group. LV end-diastolic pressure-volume curve exhibited a significant leftward shift in WT-D but not in KO-D group. LV end-diastolic diameter, percent fractional shortening, and the ratio of peak velocity of early and late filling (E/A wave) were significantly reduced in WT-D mice as analyzed by echocardiography. The increase in cardiac myocyte apoptosis and fibrosis was significantly higher in the WT-D group. Expression of atrial natriuretic peptide and transforming growth factor-beta1 was significantly increased in the WT-D group. Induction of diabetes increased protein kinase C (PKC) phosphorylation in both groups. However, phosphorylation of PKC-betaII was significantly higher in the WT-D group, whereas phosphorylation of PKC-zeta was significantly higher in the KO-D group. Levels of peroxisome proliferator-activated receptor-gamma were significantly decreased in the WT-D group but not in the KO-D group. Thus increased expression of OPN may play a deleterious role during streptozotocin-induced diabetic cardiomyopathy with effects on cardiac fibrosis, hypertrophy, and myocyte apoptosis.