Sinus node dysfunction as an initial presentation of adult systemic lupus erythematosus.

Cardiac involvement in systemic lupus erythematosus (SLE) has been well described. However, sinus node involvement with profound sinus bradycardia as an early manifestation of adult SLE has not been reported. A 27-year-old previously healthy female was admitted due to intermittent fever for 4 days. SLE was diagnosed based on clinical manifestations and laboratory data. Profound sinus bradycardia (heart rate = 41/min) with weakness was noted during hospitalization. ECG abnormalities completely resolved after a high-dose intravenous steroid infusion. Sinus node involvement with significant bradycardia is one of the possible complications in the early stage of adult SLE. Close cardiovascular monitoring and serial ECGs are suggested for early detection of this serious complication of adult SLE.

A preliminary study on the pattern of weight change from pregnancy to 6 months postpartum: a latent growth model approach.

OBJECTIVE: There is a lack of comprehensive understanding about patterns of weight change from pregnancy to childbirth and beyond. We describe the trajectory of weight change pattern from pre-pregnancy to 6 months postpartum and examine demographical and perinatal variables that predict the weight change using the latent growth model (LGM). DESIGN AND SUBJECTS: This study used a longitudinal design. The study participants were 120 women whose body weights were measured at eight time points. RESULTS: The adjusted mean pre-pregnancy weight was 52.57 kg. When the weight growth rate for 10-13 weeks of pregnancy and pre-pregnancy weight was set to 1, the body-weight change rate was 2.20 during the second trimester, 2.14 during the third trimester, -2.90 during the period from the third trimester to 2-3 weeks postpartum, -0.08 during the period from 2-3 weeks to 4-5 weeks postpartum, -0.37 during the period from 4-5 weeks to 11-12 weeks postpartum, and -0.65 during the period from 11-12 weeks to 24-25 weeks postpartum. On average, body weight increased 26.54% (13.95 kg) from pre-pregnancy to 36-39 weeks of pregnancy and body weight remained 6.26% (3.29 kg) higher at 24-25 weeks postpartum compare with pre-pregnancy. In terms of factors related to body weight, age was positively associated with pre-pregnancy body weight. Parity had a negative effect on the change of body weight. Women who had an increased change rate in body weight had higher newborn birth weights. CONCLUSIONS: We found that weight change from pregnancy to postpartum followed a pattern that could be specified using the LGM approach. The women retained more than 6% of weight at 6 months postpartum compared with their pre-pregnancy weight.

Osteopontin gene expression in the aorta and the heart of propylthiouracil-induced hypothyroid mice.

It is known that there is abnormal osteopontin (OPN) expression at the sites of atherosclerotic lesions. In the Apolipoprotein E gene knockout (ApoE-KO) mouse, a model of the atherosclerotic process, altered cholesterol metabolism with associated increase in OPN expression is evident at 12-22 weeks in the aorta and at 22 weeks in the heart. In this study, we analyzed another animal model of hypothyroid mice created by ingestion of propylthiouracil (PTU). After 2 weeks of PTU ingestion, the animals had significant decreases in thyroid hormones (T3 and T4) and immediate increases in blood lipids/cholesterol. Hypothyroid mice showed 1.3-, 1.5-, 2-fold increases in blood levels of total cholesterol, triglycerides, and low density lipoprotein-cholesterol respectively. Semi-quantitative RT-PCR analysis showed that hypothyroid mice had 1.4- to 2-fold increases of OPN mRNA expression in the aorta and 1.5-fold increases in the heart. Hypothyroid animals treated with T3 (5 microg/day for 6 days) or statin (0.2 mg/30 g for 2 weeks) reduce blood lipids and aortic OPN mRNA expression. Data obtained with ELISA analyses showed 1.5- and 1.7-fold increases in OPN protein in the aorta (10 weeks) and the heart (22 weeks), respectively. This increase is close to the mRNA expression in both tissues of hypothyroid mice. In addition, western blots showed several variants of OPN protein expressed in the aorta and the heart. The decrease in the 70 kDa OPN is accompanied by an increase in 45 kDa OPN in the aorta of hypothyroid mice. In contrast, only 45 kDa OPN is found in the heart of control and hypothyroid mice. These data indicate that the increase of OPN mRNA and protein expression occurs in cardiovascular tissues of hypothyroid mice.

Association between indices of obesity and fasting hyperglycemia in Taiwan.

OBJECTIVE: To examine the association of body mass index (BMI), waist-hip ratio (WHR), and waist circumference (WC) with fasting hyperglycemia after adjustment for age, cigarette smoking, and alcohol use. DESIGN: A cross-sectional survey was conducted among individuals visiting four health-screening centers across Taiwan. SUBJECTS: A total of 61 568 subjects (28 734 men and 32 834 women) between 25 and 64 years of age were included. Fasting hyperglycemia was defined as fasting plasma glucose > or =6.1 mmol/l or current diagnosis and use of insulin or hypoglycemic agent. RESULTS: Fasting hyperglycemia was found in 11.0% of men and 8.3% of women. The factors significantly associated with fasting hyperglycemia in men were age, BMI, WHR, and heavy drinking, while for women these factors were age, educational level, BMI, WHR, and heavy smoking. For men, increased risk of fasting hyperglycemia started from age 30 to 34 years, BMI > or =25 kg/m2, and WHR > or =0.82. For women, increased risk of fasting hyperglycemia started from age 35 to 39 years, BMI > or =24 kg/m2, and WHR > or =0.74. WC lost its significance as a predictor of fasting hyperglycemia when WHR included in the model. CONCLUSION: This study found that central obesity and general obesity were both independently associated with increased risk of fasting hyperglycemia in Taiwanese. The relationship between fasting hyperglycemia and central fat accumulation (WHR) begins to appear at levels that would not be regarded as representing obesity in Western populations, suggesting the need to redefine cutoffs for central obesity in this population.

Differential pH effect on calcium-induced conformational changes of cardiac troponin C complexed with cardiac and fast skeletal isoforms of troponin I and troponin T.

The aim of this study is to investigate the molecular events associated with the deleterious effects of acidosis on the contractile properties of cardiac muscle as in the ischemia of heart failure. We have conducted a study of the effects of increasing acidity on the Ca(2+) induced conformational changes of pyrene labelled cardiac troponin C (PIA-cTnC) in isolation and in complex with porcine cardiac or chicken pectoral skeletal muscle TnI and/or TnT. The pyrene label has been shown to serve as a useful fluorescence reporter group for conformational and interaction events of the N-terminal regulatory domain of TnC with only minimal fluorescence changes associated with C-terminal domain. Results obtained show that the significant decreases at pH 6.0 of site II Ca(2+) affinity of PIA-cTnC when complexed as a binary complex with either cTnI or cTnT are significantly reduced when cTnI is replaced with sTnI or cTnT with sTnT. However, this effect is appreciably diminished when the cTnI and cTnT in the ternary complex are replaced by sTnI and sTnT. The smaller effects in the ternary complex of replacing both cTnI and cTnT by their skeletal counterparts on depressing the Ca(2+) affinity from pH 7.0 to 6.0 arise from TnI replacement. Thus, changes in TnC conformation resulting from isoform-specific interactions with TnI and TnT could be an integral part of the effect of pH on myofilament Ca(2+)sensitivity.

Spectrofluorometric analysis of length-dependent conformational changes in cardiac troponin C.

Length modulation of cardiac muscle is manifested in the Frank-Starling relation of the heart. Recently, it has been shown that length-dependent changes in SH reactivity of cardiac troponin C (cTnC) occurred in association with cross-bridge attachment and Ca2+. However, the presence of two SH groups (Cys-35 and Cys-84) in the regulatory region of cTnC complicates efforts to detect conformational changes. In this study skinned porcine cardiac fibers were reacted with 7-diethylamino-3-[4'maleimidylphenyl]-4-methylcoumarin (CPM). Alkaline urea gel electrophoresis, along with protein elution, was used to isolate filament bound cTnC. Analysis of fluorescence measurement showed that there is a Ca(2+)-increased fluorescence for CPM-labeled cTnC in long fibers (sarcomere length = 2.2 approximately 2.5 microm) but not in short fibers (sarcomere length = 1.6 approximately 1.8 microm). In addition, the labeled cTnC was measured for the fluorescence decrease over time by adding a non-fluorescence energy acceptor, 4-dimethylaminophenylazophenyl-4'maleimide (DABMI), in the presence and absence of Ca2+. Fluorescence quenching by DABMI is not affected by Ca2+ in long fibers but it is significantly increased in short fibers. However, the fibers maintained in the relaxed state with 5 mM MgATP and 1 mM Vanadate showed no length effect on the CPM-labeled cTnC in terms of the Ca(2+)-mediated changes in fluorescence spectrum and in fluorescence quenching by DABMI. All together, our results suggest that the relative reactivities of Cys-35 and Cys-84 vary with sarcomere length.

Effects of sarcomere length and Ca(2+) binding on h reactivity of myofilament bound troponin C in porcine skinned cardiac muscle fibers.

Length dependence of cardiac Ca(2+) activation is an essential component of the Frank-Starling relation. The aim of this study is to examine the length effects on the Ca(2+)-induced conformational changes of filament-bound cTnC in skinned cardiac muscle fibers. The two cysteine residues (Cys-35 and Cys-84) in the regulatory domain of cTnC allow for the attachment of conformational probes to this region. Their incorporation with the fluorescent probe, 7-diethylamino-3-[4'-maleimidylphenyl]-4-methylcoumarin (CPM), was used to determine the varying cTnC conformations in cardiac fibers. The data obtained show that the length-dependent Ca(2+)-mediated conformational changes require strong-binding cross-bridges for cardiac activation.

Altered expression of cardiac myosin isozymes associated with the malignant hyperthermia genotype in swine.

BACKGROUND: Anesthetic-induced malignant hyperthermia (MH) in humans and pigs is associated with dramatic alterations in cardiac function. However, it remains controversial as to whether MH-associated cardiac symptoms represent a primary difference of myocardium or a secondary alteration consequent to increases in the hyperthermic stress. Here the authors describe changes in myosin isoform expression in the hearts of MH-susceptible pigs with and without prior exposure to halothane. METHODS: One group of pigs was diagnosed as MH susceptible by halothane challenge and Hal-1843 nucleotide examination. To determine if there is an effect of halothane exposure, another group of pigs was diagnosed by simple MH genotyping without exposure to halothane. After diagnosis and genotyping, animals with and without exposure to halothane were killed to study cardiac myosin isozyme distributions, cardiac myofibrillar adenosine triphosphatase (ATPase) activity, and the steepness of the Ca2+-ATPase activity relation in the hearts of normal and susceptible pigs. The altered myosin isozyme expression was analyzed by pyrophosphate gel electrophoresis. RESULTS: Malignant hyperthermia-susceptible animals with the prior halothane challenge showed an increased V1 myosin (-44%) expression, increased myofibrillar ATPase activity (-25%) and increased steepness of the Ca2+-ATPase activity relation. Without exposure to halothane, no change of myofibrillar ATPase activity was found in the hearts of different genotyped pigs, but there was a small increase in expression of V1 myosin (-5%) in the mutant (TT). CONCLUSIONS: The potential modulation of V1 myosin expression occurs in the hearts of MH-susceptible pigs. The added stress by halothane challenge would further cause a V3 --> V1 shift, which may be attributed to the long-term effects of hyperthermic stress.

The effect of thrombolytic therapy on short- and long-term cardiac autonomic activity in patients with acute myocardial infarction.

BACKGROUND: Reduced heart rate variability after acute myocardial infarction is an important risk stratification factor for mortality and life threatening ventricular arrhythmias. In recent years, thrombolytic therapy has revolutionized the therapy of acute myocardial infarction. However, there is little information about the mechanism of the beneficial effect of thrombolysis on cardiovascular mortality. This study was launched to investigate the relationship between thrombolytic therapy and cardiac autonomic activity, and the sequential changes in heart rate variability after acute myocardial infarction. METHODS: From October 1994 to July 1995, all consecutive patients with their first acute myocardial infarction were prospectively enrolled into the study. Patients without contraindication underwent thrombolytic therapy within six hours of the onset of symptoms. Other patients received conventional treatment. Ambulatory electrocardiography (EKG) was recorded on each patient 7, 90 and 180 days after acute myocardial infarction. Heart rate variability in time- and frequency-domain was analyzed. RESULTS: A total of 49 patients, 45 males and 4 females, were included in this study. The short-term heart rate variability (HRV) (seven-day) in the thrombolytic group was significantly higher than in the nonthrombolytic group in SDANN and SDNN. No significant difference in rMSSD, pNN50, LF, HF or LF/HF ratio was found. The location of MI did not influence the short-term HRV following acute myocardial infarction. In patients treated with thrombolytic agent, the follow-up HRV at 90 days and 180 days increased significantly compared to the baseline HRV (seven-day) in SDANN, SDNN, LF and HF bands. For patients without thrombolytic therapy, their follow-up HRV at 90-day and 180-day increased significantly as compared to the baseline HRV (seven-day) in SDANN and SDNN only. After correction of ventricular ejection fraction, the higher short-term (seven day) HRV activities were still present in SDANN and SDNN in patients with thrombolysis as compared to those without. The 90-day and 180-day HRV did not differ between patients with and without thrombolytic agent. Three patients died suddenly during follow-up, and all showed significantly lower values of HRV than the survivors. CONCLUSIONS: The findings of the present study suggest that 1) in patients with uncomplicated AMI, HRV was transiently reduced with progressive improvement within three months after AMI in both those with and without thrombolytic therapy, and 2) patients who had received thrombolytic treatment had more improved HRV early (seven days) after AMI than those who did not. This improvement, independent of the change of left ventricular function, could be associated with the beneficial effect of thrombolytic therapy in patients with AMI.

Redistribution of protein kinase C isoforms in association with vascular hypertrophy of rat aorta.

Freshly enzymatically isolated cells from the aorta of a rat model of vascular hypertrophy were used to investigate the role of protein kinase C (PKC) isoforms during a physiologically relevant growth response. With the combination of immunofluorescence with digital imaging microscopy, PKC isoforms alpha, delta, and zeta were found to be present in single cells from control and hypertrophied rat aortas. The alpha- and zeta-isoforms were distributed in the cytoplasm of control cells; however, in hypertrophied cells, sustained translocations of alpha-PKC to the surface membrane and zeta-PKC to the intranuclear area were seen. delta-PKC was concentrated in the perinuclear area in control cells but appeared to translocate to a more diffuse localization in the cytosol of hypertrophied cells. Staining of mitochondria with rhodamine 123 indicated some similarity in the spatial distribution compared with that of delta-PKC. In control cells, translocation of isoforms alpha and delta was activated by phenylephrine or 12-deoxyphorbol 13-isobutyrate 20-acetate. Agonist stimulation produced translocation of no isoforms in the hypertrophied cells. These results indicate that isoform-specific spatial distribution and translocation of PKC occur in association with the growth response of vascular hypertrophy.

Energy-transfer measurements of the Cys35-Cys84 distance in bovine cardiac troponin C.

Bovine cardiac troponin C (cTnC) has cysteine residues located in the non-functional Ca(2+)-binding loop I (Cys-35) and at the N-terminal end of the central helix (Cys-84) near site II, the regulatory Ca(2+)-binding site. Recently, we reported that the excimer fluorescence resulting from the dimerization of adjacent pyrene groups attached to the two Cys residues is reduced by Ca2+ binding to site II (Liou, Y.-M. and Fuchs, F. (1992) Biophys. J. 61, 892-901). This result would suggest that Ca2+ binding causes a separation of the two Cys residues, a conclusion at variance with predictions from molecular modeling studies (Herzberg, O., Moult, J. and James, M.N.G. (1986) J. Biol. Chem. 261, 2638-2644). Alternatively, the reduction in excimer fluorescence could be accounted for by an immobilization of the pyrene attached to Cys-84 by a Ca(2+)-induced hydrophobic pocket. To arrive at a more definitive interpretation of these experiments, we carried out steady-state fluorescence resonance energy-transfer measurements of the Cys35-Cys84 distance. We used three different donor-acceptor pairs: 2-(4'-(iodoacetamido)anilino) naphthalene-6-sulfonic acid (IAANS) and 4-dimethylamino-phenylazophenyl-4-maleimide (DABMI), IAANS and N-(4-(dimethyl-amino)-3,5-dinitrophenyl) maleimide (DDPM), and 5-((((2-iodoacetyl)amino)ethyl)amino)naphthalene-1-sulfonic acid (IAEDANS) and DDPM. At pCa 8.0, the distances were 23.8, 21.0, and 22.0 A with the donor-acceptor pairs, IAANS-DABMI, IAANS-DDPM and IAEDAN-DDPM, respectively. At pCa 4.0, the distances were 25.8, 24.1 and 21.2 A. The distances at pCa 8 and pCa 4.0 were not significantly altered when labeled cTnC was complexed with cardiac troponin I (cTnI). Thus, Ca2+ has little, if any, effect on the Cys35-Cys84 distance. These results are consistent with a model in which Ca2+ binding induces a separation of helices B and C from helix D, without any relative movement of the two N-terminal Ca(2+)-binding domains.

Pyrene-labeled cardiac troponin C. Effect of Ca2+ on monomer and excimer fluorescence in solution and in myofibrils.

The two cysteine residues (Cys-35 and Cys-84) of bovine cardiac troponin C (cTnC) were labeled with the pyrene-containing SH-reactive compounds, N-(1-pyrene) maleimide, and N-(1-pyrene)iodoacetamide in order to study conformational changes in the regulatory domain of cTnC associated with cation binding and cross-bridge attachment. The labeled cTnC exhibits the characteristic fluorescence spectrum of pyrene with two sharp monomer fluorescence peaks and one broad excimer fluorescence peak. The excimer fluorescence results from dimerization of adjacent pyrene groups. With metal binding (Mg2+ or Ca2+) to the high affinity sites of cTnC (sites III and IV), there is a small decrease in monomer fluorescence but no effect on excimer fluorescence. In contrast, Ca2+ binding to the low affinity regulatory (site II) site elicits an increase in monomer fluorescence and a reduction in excimer fluorescence. These results can be accounted for by assuming that the pyrene attached to Cys-84 is drawn into a hydrophobic pocket formed by the binding of Ca2+ to site II. When the labeled cTnC is incorporated into the troponin complex or substituted into cardiac myofibrils the monomer fluorescence is enhanced while the excimer fluorescence is reduced. This suggests that the association with other regulatory components in the thin filament might influence the proximity (or mobility) of the two pyrene groups in a way similar to that of Ca2+ binding. With the binding of Ca2+ to site II the excimer fluorescence is further reduced while the monomer fluorescence is not changed significantly. In myofibrils, cross-bridge detachment (5 mM MgATP, pCa 8.0) causes a reduction in monomer fluorescence but has no effect on excimer fluorescence. However, saturation of the cTnC with Ca2+ reduces excimer fluorescence but causes no further change in monomer fluorescence. Thus, the pyrene fluorescence spectra define the different conformations of cTnC associated with weak-binding, cycling, and rigor cross-bridges.

The reactivity of sulfhydryl groups of bovine cardiac troponin C.

Bovine cardiac troponin C (cTnC) contains 2 cysteine residues, Cys-35 located in the nonfunctional Ca2+-binding loop I and Cys-84 in the N-terminal segment of the central helix. We have studied the reactivity of Cys residues in cTnC with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin (CPM). The latter compound fluoresces only when reacted with the protein. The reaction with DTNB followed second order kinetics with respect to DTNB, the rate constants being 3.37 s-1 M-1 and 1.82 s-1 M-1 in the presence and absence of Ca2+, respectively. These rates are much slower than the rate of reaction with Cys-98 of skeletal TnC (sTnC) or with the urea-denatured cTnC, indicating that both Cys residues are partly buried within the structure of the protein. The increase in reactivity was induced by binding of Ca2+ to the single low affinity Ca2+ binding site (site II). The fluorescence increase upon reaction of cTnC with CPM in the absence of Ca2+ could be fitted with a single exponential equation indicating that both cysteine residues are equally available to the reagent. The reaction in the presence of Ca2+ was biphasic. Analysis of CNBr fragments of cTnC labeled with CPM under various conditions indicated that in the presence of Ca2+ the reactivity of Cys-84 is increased while that of Cys-35 is slightly decreased. This finding is consistent with the model of Herzberg et al. (Herzberg, O., Moult, J., and James, M. N. G. (1986) J. Biol. Chem. 261, 2638-2644) and the data of Ingraham and Hodges (Ingraham, R. H., and Hodges, R. S. (1988) Biochemistry 27, 5891-5898), suggesting that the Ca2+-induced conformational change in the N-terminal half of TnC involves separation of the helix C from the central helix, thereby increasing the accessibility of Cys-84. The slow overall kinetics, however, indicates that the structure in the vicinity of Cys residues is relatively compact regardless of Ca2+. We interpret the increase in reactivity towards CPM as consistent with a Ca2+-induced exposure of a hydrophobic pocket in the vicinity of Cys-84.