Roles of creatine in the regulation of cardiac protein synthesis

The observation that increased muscular activity leads to muscle hypertrophy is well known, but identification of the biochemical and physiological mechanisms by which this occurs remains an important problem. Experiments have been described (5, 6) which suggest that creatine, an end product of contraction, is involved in the control of contractile protein synthesis in differentiating skeletal muscle cells and may be the chemical signal coupling increased muscular activity and the increased muscular mass. During contraction, the creatine concentration in muscle transiently increases as creatine phosphate is hydrolyzed to regenerate ATP. In isometric contraction in skeletal muscle for example, Edwards and colleagues (3) have found that nearly all of the creatine phosphate is hydrolyzed. In this case, the creatine concentration is increased about twofold, and it is this transient change in creatine concentration which is postulated to lead to increased contractile protein synthesis. If creatine is found in several intracellular compartments, as suggested by Lee and Vissher (7), local changes in concentration may be greater then twofold. A specific effect on contractile protein synthesis seems reasonable in light of the work of Rabinowitz (13) and of Page et al. (11), among others, showing disproportionate accumulation of myofibrillar and mitochondrial proteins in response to work-induced hypertrophy and thyroxin-stimulated growth. Previous experiments (5, 6) have shown that skeletal muscles cells which have differentiated in vitro or in vivo synthesize myosin heavy-chain and actin, the major myofibrillar polypeptides, faster when supplied creatine in vitro. The stimulation is specific for contractile protein synthesis since neither the rate of myosin turnover nor the rates of synthesis of noncontractile protein and DNA are affected by creatine. The experiments reported in this communication were undertaken to test whether creatine selectively stimulates contractile protein synthesis in heart as it does in skeletal muscle.     

Studies on the Protection Test of Pertussis Vaccine. Immunization Period and Protectivity

In order to confirm the data reported in the previous papers, variously prepared pertussis vaccines were employed in the present investigation. Pertussis organisms grown either on a solid or in a liquid semisynthetic medium were treated by: (1) heating at 56 C for 30 min, (2) storage in 0.1% formalin at 37 C for 5 days, (3) storage in 0.1% formalin at 25 C for 5 days, and (4) simple addition of sodium ethyl-mercuri thiosalicylate (merthiolate) as a preservative. Freeze-dried vaccines were made from these preparations four and a half months later. Mice were immunized intraperitoneally and challenged intracerebrally with a virulent strain of Bordetella pertussis 10 or 17 days later. The data were analyzed statistically assuming the probit corresponding to the percentage of survivors at any dose be a linear function of the logarithms of the dose. The 50% effective doses (ED₅₀) and slopes of each vaccine were found to be uniform. More accurate estimates of ED₅₀ were obtained by employing a pooled slope in each experiment. From these ED₅₀ values, the relative potency was estimated by comparing the value of a vaccine to that of a dried merthiolate-vaccine. For vaccines derived from solid cultures, with an immunization period of 17 days, the relative potency of the vaccine heated at 56 C was 0.63 (95% fiducial limits=0.52 to 0.76); the value for the formalinized vaccine at 37 C was 0.40 (0.30 to 0.53) and one at 25 C was 0.51 (0.34 to 0.77). Vaccines derived from liquid cultures showed a relative potency of 20 to 50% less than that of corresponding vaccine derived from a solid culture. The potency obtained for the 17 day immunization period was usually higher than that for the 10 day period. Using the overall-pooled slope, an experimental design which will be appropriate for statistical analysis is discussed.     

Accuracy of specimen-specific nonlinear finite element analysis for evaluation of radial diaphysis strength in cadaver material

The feasibility of a user-specific finite element model for predicting the in situ strength of the radius after implantation of bone plates for open fracture reduction was established. The effect of metal artifact in CT imaging was characterized. The results were verified against biomechanical test data. Fourteen cadaveric radii were divided into two groups: (1) intact radii for evaluating the accuracy of radial diaphysis strength predictions with finite element analysis and (2) radii with a locking plate affixed for evaluating metal artifact. All bones were imaged with CT. In the plated group, radii were first imaged with the plates affixed (for simulating digital plate removal). They were then subsequently imaged with the locking plates and screws removed (actual plate removal). Fracture strength of the radius diaphysis under axial compression was predicted with a three-dimensional, specimen-specific, nonlinear finite element analysis for both the intact and plated bones (bones with and without the plate captured in the scan). Specimens were then loaded to failure using a universal testing machine to verify the actual fracture load. In the intact group, the physical and predicted fracture loads were strongly correlated. For radii with plates affixed, the physical and predicted (simulated plate removal and actual plate removal) fracture loads were strongly correlated. This study demonstrates that our specimen-specific finite element analysis can accurately predict the strength of the radial diaphysis. The metal artifact from CT imaging was shown to produce an overestimate of strength.     

Electrocardiograms Corresponding to the Development of Myocardial Infarction in Anesthetized WHHLMI Rabbits (Oryctolagus cuniculus), an Animal Model for Familial Hypercholesterolemia

The aim of this study was to determine whether features indicative of myocardial ischemia occur in the electrocardiograms (ECG) in myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits, an animal model for human familial hypercholesterolemia. ECG were recorded in 110 anesthetized WHHLMI rabbits (age, 10 to 39 mo) by using unipolar and bipolar limb leads with or without chest leads. We noted the following electrocardiographic changes: T wave inversion (37.4%), ST segment depression (31.8%), deep Q wave (16.3%), reduced R wave amplitude (7.3%), ST segment elevation (2.7%), and high T wave (1.8%). These ECG changes resembled those in human patients with coronary heart disease. Histopathologic examination revealed that the left ventricular wall showed acute myocardial lesions, including loss of cross-striations, vacuolar degeneration, coagulation necrosis of cardiac myocytes, and edema between myofibrils, in addition to chronic myocardial lesions such as myocardial fibrosis. The coronary arteries that caused these ECG changes were severely stenosed due to atherosclerotic lesions. Ischemic ECG changes corresponded to the locations of the myocardial lesions. Normal ECG waveforms were similar between WHHLMI rabbits and humans, in contrast to the large differences between rabbits and mice or rats. In conclusion, ischemic ECG changes in WHHLMI rabbits reflect the location of myocardial lesions, making this model useful for studying coronary heart disease.Abbreviations: CHD, coronary heart disease; ECG, electrocardiogram; WHHL, Watanabe heritable hyperlipidemic; WHHLMI, myocardial infarction-prone Watanabe heritable hyperlipidemicCoronary heart disease (CHD) is prevalent in developed countries, including the United States.^16,24 Although potent compounds (for example, statins to inhibit cholesterol synthesis) have been developed to reduce the public health burden of this disease, CHD remains a leading cause of death, and further efforts are needed to reduce associated morbidity and mortality.²⁵ In evaluating the therapeutic effects of CHD interventions, the electrocardiogram (ECG) is an essential tool for examining myocardial function.³⁹In humans, various ischemic ECG changes occur in association with myocardial ischemia and infarction, such as high T wave, ST segment elevation, emergence of the deep Q wave, reduction of R wave amplitude, resolution of ST segment elevation, and T wave inversion.^21,39 In addition, ST segment depression is a typical change observed with subendocardial ischemia.^2,7In the study of myocardial ischemia, animal models that show ECG waveforms comparable to those of human patients with CHD play an important role. This similarity is important not only for assessing the effects of agents for the treatment of CHD but also for assessing adverse effects of newly developed agents on cardiac function. Although ECG have been used to study myocardial ischemia in several species including pigs, dogs, rabbits, rats, and mice,^{3,9,10,14,18,23} most of these studies used coronary ligation models. These models do not fully reflect the events that occur during myocardial ischemia caused by atherosclerotic coronary stenosis, which is seen typically in patients with CHD.The Watanabe heritable hyperlipidemic (WHHL) rabbit⁴⁰ and the myocardial infarction-prone WHHL (WHHLMI) rabbit³³ are animal models for the study of human myocardial ischemia. WHHLMI rabbits spontaneously develop hypercholesterolemia due to a deficiency of receptors for low-density lipoproteins and manifest severe coronary atherosclerosis and myocardial infarction. Importantly, lipoprotein metabolism in WHHL and WHHLMI rabbits resembles that in humans.^28,30 Using these advantages of the WHHL and WHHLMI models, we and others have been studying the effects of hypocholesterolemic and antiatherosclerotic agents on coronary atherosclerosis.^29,32,34 However, ECG were not examined in these studies. Because the rabbit heart is electrophysiologically similar to the human heart,^27,38 using ECG to monitor myocardial function in the WHHLMI rabbit may be valuable.In the present study, we examined whether ECG changes observed in WHHLMI rabbits reflect myocardial ischemia and whether those changes correspond to ECG features in human patients with CHD.     

Weight loss improves neurovascular and muscle metaboreflex control in obesity

We studied the effects of a hypocaloric diet (D, n = 24, age: 32.2 +/- 1.4 yr, body mass index: 34.7 +/- 0.5 kg/m2) and a hypocaloric diet associated with exercise training (D + T, n = 25, age: 32.3 +/- 1.3 yr, body mass index: 32.9 +/- 0.4 kg/m2) on muscle metaboreflex control, muscle sympathetic nerve activity (MSNA, microneurography), blood pressure, and forearm blood flow (plethysmography) levels during handgrip exercise at 10% and 30% of maximal voluntary contraction in normotensive obese women. An additional 10 women matched by age and body mass index were studied as a nonadherent group. D or D + T significantly decreased body mass index. D or D + T significantly decreased resting MSNA (bursts/100 heartbeats). The absolute levels of MSNA were significantly lower throughout 10% and 30% exercise after D or D + T, although no change was found in the magnitude of response of MSNA. D + T, but not D, significantly increased resting forearm vascular conductance. D + T significantly increased the magnitude of the response of forearm vascular conductance during 30% exercise. D or D + T significantly increased MSNA levels during posthandgrip circulatory arrest when muscle metaboreflex is isolated. In conclusion, weight loss improves muscle metaboreflex control in obese women. Weight loss reduces MSNA, which seems to be centrally mediated. Weight loss by D + T increases forearm vascular conductance at rest and during exercise in obese individuals.     

Clinical significance of urinary N1,N12-diacetylspermine levels in patients with hepatocellular carcinoma

BACKGROUND/AIM: N1,N12-diacetylspermine (DiAcSpm), a diacetylpolyamine which was recently identified in urine, appeared to be a useful tumor marker for urogenital cancers. Here we examined the clinical significance of urinary DiAcSpm as a tumor marker for hepatocellular carcinoma (HCC). METHODS: Urine samples were collected from patients with HCC and benign liver diseases. Urinary levels of DiAcSpm were measured by ELISA, which was newly developed in order to analyze large numbers of samples. RESULTS: The appropriate threshold value was set at 325 nM/g x creatinine. The sensitivity of the DiAcSpm assay for HCC was 65.5% and the specificity calculated between HCC and liver cirrhosis was 76.0%. The percentage of DiAcSpm-positive HCC patients was similar to that for AFP or PIVKA-II. At more advanced clinical stages, the positive percentage of these three markers increased but the DiAcSpm levels appeared to move independently of AFP and PIVKA-II. In HCC patients, the DiAcSpm levels reflected the progression of disease or the effect of treatment. CONCLUSIONS: DiAcSpm levels were found to reflect the severity, activity or viability of HCC. Urinary DiAcSpm can therefore be considered one of the useful indexes for patients with HCC.     

Arginine methylation analysis of the splicing-associated SR protein SFRS9/SRP30C

The human SFRS9/SRp30c belongs to the SR family of splicing regulators. Despite evidence that members of this protein family may be targeted by arginine methylation, this has yet to be experimentally addressed. In this study, we found that SFRS9 is a target for PRMT1-mediated arginine methylation in vitro, and that it is immunoprecipitated from HEK-293 lysates by antibodies that recognize both mono- and dimethylated arginines. We further observed that upon treatment with the methylation inhibitor Adox, the fluorescent EGFP-SFRS9 re-localizes to dot-like structures in the cell nucleus. In subsequent confocal analyses, we found that EGFP-SFRS9 localizes to nucleoli in Adox-treated cells. Our findings indicate the importance of arginine methylation for the subnuclear localization of SFRS9.     

Transbilayer movement of Glc-P-dolichol and its function as a glucosyl donor: protein-mediated transport of a water-soluble analog into sealed ER vesicles from pig brain

The results described in the accompanying article support the model in which glucosylphosphoryldolichol (Glc-P-Dol) is synthesized on the cytoplasmic face of the ER, and functions as a glucosyl donor for three Glc-P-Dol:Glc0-2Man9-GlcNAc2-P-P-Dol glucosyltransferases (GlcTases) in the lumenal compartment. In this study, the enzymatic synthesis and structural characterization by NMR and electrospray-ionization tandem mass spectrometry of a series of water-soluble beta-Glc-P-Dol analogs containing 2-4 isoprene units with either the cis - or trans - stereoconfiguration in the beta-position are described. The water- soluble analogs were (1) used to examine the stereospecificity of the Glc-P-Dol:Glc0-2Man9GlcNAc2-P-P-Dol glucosyltransferases (GlcTases) and (2) tested as potential substrates for a membrane protein(s) mediating the transbilayer movement of Glc-P-Dol in sealed ER vesicles from rat liver and pig brain. The Glc-P-Dol-mediated GlcTases in pig brain microsomes utilized [3H]Glc-labeled Glc-P-Dol10, Glc-P-(omega, c )Dol15, Glc-P(omega, t,t )Dol20, and Glc-P-(omega, t,c )Dol20as glucosyl donors with [3H]Glc3Man9GlcNAc2-P-P-Dol the major product labeled in vitro. A preference was exhibited for C15-20 substrates containing an internal cis -isoprene unit in the beta-position. In addition, the water-soluble analog, Glc-P-Dol10, was shown to enter the lumenal compartment of sealed microsomal vesicles from rat liver and pig brain via a protein-mediated transport system enriched in the ER. The properties of the ER transport system have been characterized. Glc- P-Dol10was not transported into or adsorbed by synthetic PC-liposomes or bovine erythrocytes. The results of these studies indicate that (1) the internal cis -isoprene units are important for the utilization of Glc-P-Dol as a glucosyl donor and (2) the transport of the water- soluble analog may provide an experimental approach to assay the hypothetical "flippase" proposed to mediate the transbilayer movement of Glc-P-Dol from the cytoplasmic face of the ER to the lumenal monolayer.