tbuckley/cabot-search huggingface dataset:
Characteristics of sarcomere shortening in single frog atrial cardiac cells during lightly loaded contractions.
Authors: MTarr, J WTrank, PLeiffer
Journal: Circulation Research (1981)

We studied sarcomere performance in single isolated intact cardiac cells using techniques that allow direct measurement of sarcomere length and force. This investigation dealt primarily with sarcomere performance during twitch contractions under lightly loaded conditions. In such contractions, there was a significant portion of the contraction in which sarcomere shortening occurred at constant velocity over a significant range of sarcomere lengths. The constant velocity phase of shortening was followed by a phase of shortening in which sarcomere velocity decreased markedly. Both the velocity and extent of sarcomere shortening depended on the stimulus parameters used to excite the cell. With threshold stimulation, sarcomere velocities during the constant velocity phase of shortening ranged from 1 to 5.5 micron/sec in different cells and significant slowing of sarcomere shortening began at sarcomere lengths of 1.8-2.0 micron. In contrast, when cells were stimulated with a long duration stimulus (200 msec) o...
Decreased intercellular coupling after prolonged rapid stimulation in rabbit atrial muscle.
Authors: JBredikis, FBukauskas, RVeteikis
Journal: Circulation Research (1981)

Driving rabbit atrial trabeculae at a rapid rate for 15 minutes resulted in a decrease in the space constant for electrotonic decay from an average of 670 to 440 micrometers. Input resistance, Rin, as measured by use of a double-barrelled microelectrode, increased from a mean value of 380 kOhms to one of 600 kOhms. The time to return to control values after the end of rapid driving was 20-60 minutes. Similar effects of rapid driving were observed in the presence of atropine, propranolol, and atropine plus propranolol and phentolamine. According to the theory of current spread in a three-dimensional syncytium, a rise of input resistance should be interpreted mainly as an increase of cell-to-cell resistance. We advance the hypothesis that, when driven at their maximal possible rate (or when fibrillating), cardiac cells gain Na+ ad Ca2+, and that this results in partial but reversible uncoupling.
In vitro effects of a recombinant toxin targeted to the fibroblast growth factor receptor on rat vascular smooth muscle and endothelial cells.
Authors: SBiro, C BSiegall, Y MFu, ESpeir, IPastan, S EEpstein
Journal: Circulation Research (1992)

The dominant mechanism responsible for restenosis after angioplasty is believed to be the activation of medial smooth muscle cells (SMCs), leading to their proliferation, migration to the subintima, and further proliferation. To develop novel strategies that might inhibit or prevent restenosis, we previously used a chimeric toxin composed of transforming growth factor-alpha (which targets the epidermal growth factor receptor) and mutated Pseudomonas exotoxin to preferentially recognize and kill rapidly proliferating, versus quiescent, vascular SMCs. We have recently cloned and expressed a recombinant gene encoding Pseudomonas exotoxin with a mutated (nonfunctional) cell recognition domain fused with the ligand acidic fibroblast growth factor, termed aFGF-PE66(4Glu)KDEL; thus, this recombinant toxin targets the fibroblast growth factor receptor. In the present study, we evaluated the relative effects of this chimeric toxin on quiescent versus rapidly proliferating vascular SMCs and also determined whether ...
Effects of magnesium on the tone of isolated human coronary arteries. Comparison with diltiazem and nitroglycerin.
Authors: TKimura, HYasue, NSakaino, MRokutanda, MJougasaki, HAraki
Journal: Circulation (1989)

To study the effects of magnesium (Mg2+) on human coronary arteries and to compare those effects with those of diltiazem and nitroglycerin, we measured the tension of ring segments from isolated human coronary arteries obtained at autopsy within 5 hours after death. Precontracted segments with 3 x 10(-6) M prostaglandin F2 alpha were studied after adding cumulative concentrations of these agents (1.0-8.0 mM, 10(-9)-10(-5) M, and 10(-10)-10(-6) M, respectively). Mg2+ significantly inhibited the tonic contraction compared with the time-matched controls at 1.0 and 2.0 mM (48.7 +/- 5.6% vs. 88.6 +/- 2.2%, p less than 0.01, 36.2 +/- 6.1% vs. 78.9 +/- 3.0%, p less than 0.01, respectively). 1.0 and 2.0 mM Mg2+ did not suppress, but actually increased, the amplitude of periodic contraction, but 8.0 mM Mg2+ reduced the amplitude compared with the controls (6.6 +/- 5.2% vs. 73.3 +/- 10.7%, p less than 0.01). Diltiazem at a concentration of 10(-5) M moderately inhibited the tonic contraction, and reduced the amplitu...
Sequence and magnitude of ventricular volume changes in painful and painless myocardial ischemia.
Authors: G JDavies, WBencivelli, GFragasso, SChierchia, FCrea, JCrow, P ACrean, TPratt, MMorgan, AMaseri
Journal: Circulation (1988)

Stimulation of left ventricular stretch receptors has been proposed as a possible mechanism for the occurrence of cardiac pain. Changes in left ventricular volume were continuously assessed in 12 patients during 11 spontaneous (two painful) and 12 ergometrine-induced (nine painful) ischemic attacks with a precordial scintillation probe and blood pool labeling with technetium-99m. In all ischemic episodes, spontaneous or induced, painful or painless, severe dilatation of the left ventricle was consistently observed. These changes always preceded the onset of ST segment shifts and occurred long before pain, when present. The maximum increase in end-diastolic volume was slightly greater in painful than in painless episodes, 38 +/- 8.0% versus 28 +/- 12.4%, but no significant difference was observed in the rate of volume change or in the maximum increase of end-systolic volume (133 +/- 50% and 110 +/- 27.3%), stroke volume (-28 +/- 15% and -25 +/- 12.4%), or ejection fraction (-32 +/- 8.7% and -26 +/- 6.0%). ...
Measurement of angiotensin I converting enzyme inhibition in the heart.
Authors: AKinoshita, HUrata, F MBumpus, AHusain
Journal: Circulation Research (1993)

Angiotensin (Ang) I converting enzyme (ACE) inhibitors represent a major advance in the treatment of congestive heart failure, and tissue, rather than circulating ACE, may be their major site of action. However, assessments of tissue ACE inhibition in treated patients has not always supported this contention. In these studies, ACE activity was measured in homogenates of sampled tissue by biochemical methods. In the present study, using a model system, we have examined the validity of these tissue-sampling methods. Functional ACE activity was determined by comparing positive inotropic responses to [Pro10]Ang I in either vehicle-pretreated or ACE inhibitor-pretreated papillary muscles. [Pro10]Ang I elicits a response, which is entirely dependent on ACE-mediated conversion to Ang II. The ACE inhibitors studied were captopril, enalaprilat, lisinopril, and quinaprilat. In a parallel study, papillary muscle ACE activity was also measured in homogenates using [125I]MK-351A (a radiolabeled ACE inhibitor) binding....
The failing human heart is unable to use the Frank-Starling mechanism.
Authors: R HSchwinger, MBöhm, AKoch, USchmidt, IMorano, H JEissner, PUberfuhr, BReichart, EErdmann
Journal: Circulation Research (1994)

There is evidence that the failing human left ventricle in vivo subjected to additional preload is unable to use the Frank-Starling mechanism. The present study compared the force-tension relation in human nonfailing and terminally failing (heart transplants required because of dilated cardiomyopathy) myocardium. Isometric force of contraction of electrically driven left ventricular papillary muscle strips was studied under various preload conditions (2 to 20 mN). To investigate the influence of inotropic stimulation, the force-tension relation was studied in the presence of the cardiac glycoside ouabain. In skinned-fiber preparations of the left ventricle, developed tension was measured after stretching the preparations to 150% of the resting length. To evaluate the length-dependent activation of cardiac myofibrils by Ca2+ in failing and nonfailing myocardium, the tension-Ca2+ relations were also measured. After an increase of preload, the force of contraction gradually increased in nonfailing myocardium...
Re: Multicenter Prospective Randomized Study of Single-incision Mini-sling vs Tension-free Vaginal Tape-obturator in Management of Female Stress Urinary Incontinence: A Minimum of 1-year Follow-up
Authors: Maurizio Serati, Andrea Braga, Paola Sorice, Maria Carmela Di Dedda, Fabio Ghezzi
Journal: European Urology (2013)
The hemodynamic effects of sympathetic stimulation combined with parasympathetic blockade in man.
Authors: J RStratton, M APfeifer, J BHalter
Journal: Circulation (1987)

To define the effects of circulating norepinephrine and epinephrine on cardiac function and to determine whether left ventricular function is influenced by parasympathetic mechanisms during catecholamine stimulation, hemodynamic changes were investigated in healthy young human subjects who were supine and awake during infusion of intravenous norepinephrine alone (125 ng/kg/min) (n = 6), norepinephrine (125 ng/kg/min) plus epinephrine (50 ng/kg/min) (n = 6), and norepinephrine plus epinephrine plus parasympathetic blockade induced by atropine (2 mg intravenously) (n = 5). Ejection fraction and changes in cardiac volumes were measured by radionuclide ventriculography. During the infusion of norepinephrine plus epinephrine, plasma norepinephrine increased from 358 +/- 35 to 1782 +/- 123 pg/ml (mean +/- SE) and plasma epinephrine increased from 31 +/- 5 to 355 +/- 90 pg/ml (both p less than .01 vs baseline). These increases in plasma catecholamines were associated with increases in the heart rate (58 +/- 3 to...
Beneficial effect of carnitine on mechanical recovery of rat hearts reperfused after a transient period of global ischemia is accompanied by a stimulation of glucose oxidation.
Authors: T LBroderick, H AQuinney, C CBarker, G DLopaschuk
Journal: Circulation (1993)

BACKGROUNDWe have previously shown that increasing myocardial carnitine levels in fatty acid-perfused isolated working rat hearts dramatically increases glucose oxidation rates. Since high levels of fatty acids depress reperfusion recovery of ischemic hearts by inhibiting glucose oxidation, we determined what effect carnitine has on glucose oxidation during reperfusion of ischemic hearts.METHODS AND RESULTSIsolated working rat hearts were perfused with 11 mM [5-3H/ul-14C]glucose, 1.2 mM palmitate, and 100 microU/ml insulin and subjected to a 35-minute period of global ischemia followed by aerobic reperfusion. Rates of glycolysis and glucose oxidation were determined by measuring tritiated water and 14CO2 production, respectively. Before ischemia, myocardial carnitine content was first increased by perfusing hearts during a 60-minute baseline aerobic perfusion with 10 mM L-carnitine. This resulted in a significant increase in total myocardial carnitine from 4,804 +/- 358 to 9,692 +/- 2,090 nmol/g dry wt (m...
Overdrive suppression of conduction at the canine Purkinje-muscle junction.
Authors: R FGilmour, J RDavis, D PZipes
Journal: Circulation (1987)

We have shown previously that overdrive suppression of conduction in depolarized His-Purkinje tissue requires conduction asymmetry. In this study we examined whether overdrive suppression of conduction can occur at the Purkinje-muscle junction, where natural asymmetry of conduction exists. Canine Purkinje-muscle preparations were superfused with hyperkalemic Tyrode's solution (KCl 8 to 12 mM), and action potentials were recorded from Purkinje, junctional, and muscle cells. Initially, the Purkinje fiber was paced at the shortest cycle length at which 1:1 anterograde Purkinje-muscle conduction occurred. The papillary muscle then was paced for 10 to 50 beats at shorter cycle lengths during which, because of conduction asymmetry at the Purkinje-muscle junction, 1:1 retrograde muscle-Purkinje conduction also occurred. After overdrive papillary muscle pacing, Purkinje fiber pacing at the same cycle length that previously resulted in 1:1 conduction now produced transient Purkinje-muscle conduction block (overdri...
Exercise-induced hypotension in a male population. Criteria, causes, and prognosis.
Authors: PDubach, V FFroelicher, JKlein, DOakes, MGrover-McKay, RFriis
Journal: Circulation (1988)

The objective of this study was to demonstrate the causes, optimal definition, and predictive value of exercise-induced hypotension occurring during treadmill testing. This study included all patients referred for clinical reasons to the Long Beach Veterans Administration Medical Center treadmill laboratory and then followed for a 2-year period for cardiac events. The population consisted of 2,036 patients who underwent testing from April 4, 1984, to May 7, 1987, 131 of whom exhibited exercise-induced hypotension (6.4%). We found that exercise-induced hypotension is usually related to myocardial ischemia or myocardial infarction, is best defined as a drop in systolic blood pressure during exercise below the standing preexercise value, and indicates a significantly increased risk for cardiac events (3.2-fold, p less than 0.005). This increased risk was not found in those having no previous myocardial infarction or no signs or symptoms of ischemia during the exercise test, and the increased risk was also no...
Relationship between atopic dermatitis, depression and anxiety: a two‐sample Mendelian randomization study
Authors: H. Baurecht, C. Welker, S.‐E. Baumeister, S. Weidnger, C. Meisinger, M.F. Leitzmann, H. Emmert
Journal: British Journal of Dermatology (2021)

Growing evidence suggests that atopic dermatitis (AD) is associated with an increased risk of depressive disorders and anxiety. However, existing studies were observational and may have uncovered correlations but could not easily disentangle noncausal or reverse-causal associations because these associations could be confounded and may not reflect true causal relationships.To examine, in a two-sample Mendelian randomization study, the potential effect of AD on the risk of depressive disorders and anxiety.Genetic instruments from the largest available genome-wide association study (GWAS) for AD (10 788 cases and 30 047 controls) were used to investigate the relationship to broad depression (170 756 cases and 329 443 controls), major depressive disorder (MDD; 30 603 cases and 143 916 controls) and anxiety (5580 cases and 11 730 controls). A set of complementary approaches were carried out to assess horizontal pleiotropy and related potential caveats occurring in MR studies.We observed no causal impact of AD on the risk of depressive disorders and anxiety, with close-to-zero effect estimates. The inverse weighted method revealed no associations of AD on broad depression [odds ratio (OR) 1·014; P = 0·431], probable MDD (OR 1·002; P = 0·568), International Classification of Diseases, Ninth/Tenth Revision-based MDD (OR 1·001; P = 0·466) or anxiety (OR 1·097; P = 0·180).This MR study does not support a causal effect of AD on depression and anxiety.
Nifedipine therapy for patients with threatened and acute myocardial infarction: a randomized, double-blind, placebo-controlled comparison.
Authors: J EMuller, JMorrison, P HStone, R ERude, BRosner, RRoberts, D LPearle, Z GTuri, J FSchneider, D HSerfas
Journal: Circulation (1984)

Preliminary clinical and laboratory observations suggest that nifedipine might prevent progression of threatened myocardial infarction by reversing coronary spasm or might limit necrosis during the course of acute myocardial infarction. We screened 3143 patients with ischemic pain of greater than 45 min duration and randomly assigned 105 eligible patients with threatened myocardial infarction and 66 with acute myocardial infarction to receive nifedipine (20 mg orally every 4 hr for 14 days) or placebo plus standard care. Treatment was started 4.6 +/- 0.1 hr after the onset of pain. Infarct size index was calculated by the MB-creatine kinase (CK) method and expressed as CK-geq/m2 +/- SE. The incidence of progression to infarction among patients with threatened myocardial infarction was not significantly altered by nifedipine (36 of 48 [75%] for placebo-treated and 43 of 57 [75%] for nifedipine-treated patients). Furthermore, infarct size index was similar among placebo- and nifedipine-treated patients (16....
Effects of spontaneous respiration on left ventricular function assessed by echocardiography.
Authors: KAndersen, HVik-Mo
Journal: Circulation (1984)

The effects of quiet respiration on assessment of left ventricular function by two-dimensional echocardiography were investigated in 12 healthy men. End-diastolic area in the parasternal short-axis view decreased with inspiration (from 17.3 +/- 2.1 [mean +/- SD] to 16.0 +/- 2.1 cm2, p less than .01), while end-systolic area did not change (from 7.6 +/- 1.4 to 7.7 +/- 1.5 cm2; NS). A fixed cursor that was located through the center of the left ventricular area at end-expiration made a tangential cut of the area at end-inspiration were smaller along the cursor than through the center of the short-axis area both at end-diastole (1.9 +/- 1.7 mm; p less than .01) and end-systole (3.8 +/- 4.0 mm; p less than .01). Our results suggest a need for standardization with regard to respiratory phases in assessment of left ventricular function by two-dimensional echocardiography and indicate the occurrence of inspiratory reduction of left ventricular stroke volume associated with decreased diastolic filling. Motion of ...
The role of intracoronary thrombus in unstable angina: angiographic assessment and thrombolytic therapy during ongoing anginal attacks.
Authors: KGotoh, TMinamino, OKatoh, YHamano, SFukui, MHori, HKusuoka, MMishima, MInoue, TKamada
Journal: Circulation (1988)

Intracoronary thrombus is regarded as a potentially important factor in the etiology of unstable angina, but the incidence of intracoronary thrombus in unstable angina has not been clearly defined. To determine the occurrence of intracoronary thrombus during ongoing angina pectoris, coronary angiography was performed during spontaneous ischemic attacks in 37 patients with prolonged rest angina. All patients exhibited significant (greater than 50%) stenoses of at least one major coronary artery. Of the 37 patients, 21 (57%) had intracoronary thrombus in major coronary arteries, whereas 14 (38%) had fixed narrowings without evidence of intracoronary thrombus and two exhibited coronary spasm. ST segment elevation was observed in 16 of 21 patients with thrombus and in all of the patients with coronary spasm, but all the patients with organic stable obstruction showed ST segment depression. Twenty of the 21 patients with thrombus improved after thrombolytic therapy with intracoronary injection of urokinase; ob...
Quantitative Microbial Risk Assessment for Airborne Transmission of SARS-CoV-2 via Breathing, Speaking, Singing, Coughing, and Sneezing
Authors: Jack Schijven, Lucie C. Vermeulen, Arno Swart, Adam Meijer, Erwin Duizer, Ana Maria de Roda Husman
Journal: Environmental Health Perspectives (2021)

Background: Evidence for indoor airborne transmission of SARS-CoV-2 is accumulating. Objectives: We assessed of the risk of illness due to airborne SARS-CoV-2 particles from breathing, speaking, singing, coughing, and sneezing in indoor environments. Methods: A risk assessment model, AirCoV2, for exposure to SARS-CoV-2 particles in aerosol droplets was developed. Previously published data on droplets expelled by breathing, speaking, singing, coughing, and sneezing by an infected person were used as inputs. Scenarios encompassed virus concentration, exposure time, and ventilation. Newly collected data of virus RNA copies in mucus from patients are presented. Results: The expelled volume of aerosols was highest for a sneeze, followed by a cough, singing, speaking, and breathing. After 20 min of exposure, at 107 RNA copies/mL in mucus, all mean illness risks were largely estimated to be below 0.001, except for the "high" sneeze scenario. At virus concentrations above 108 RNA copies/mL, and after 2 h of exposure, in the high and "low" sneeze scenarios, the high cough scenario and the singing scenario, risks exceeded 0.01 and may become very high, whereas the low coughing scenario, the high and low speaking scenarios and the breathing scenario remained below 0.1. After 2 h of exposure, singing became the second highest risk scenario. One air exchange per hour reduced risk of illness by about a factor of 2. Six air exchanges per hour reduced risks of illness by a factor of 8–13 for the sneeze and cough scenarios and by a factor of 4–9 for the other scenarios. Discussion: The large variation in the volume of expelled aerosols is discussed. The model calculations indicated that SARS-CoV-2 transmission via aerosols outside of the 1.5-m social distancing norm can occur. Virus concentrations in aerosols and/or the amount of expelled aerosol droplets need to be high for substantial transmission via this route. AirCoV2 is made available as interactive computational tool. https://doi.org/10.1289/EHP7886
Effects of physical training on myocardial vascularity and perfusion.
Authors: JScheuer
Journal: Circulation (1982)

Physical training is thought to be a stimulus for coronary vascular growth and coronary collateral development. This report is a summary of knowledge in the area. Studies in experimental animals with normal hearts indicate that physical training promotes increased myocardial capillary density and also causes enlargement of the surface coronary vessels. The physiologic effect of these changes on coronary vascular reserve and protection of segments of the heart against myocardial ischemia has not been established. Physically trained dogs and pigs do not appear to be protected against the effects of coronary occlusion, in that the ischemic area appears to be as large in trained animals as in untrained animals for any given coronary lesion. One study in physically trained rats appears to show protection against myocardial infarction, but whether this is related to coronary vascular changes has not been established. Experiments in dogs subjected to chronic narrowing or gradual occlusion demonstrate that physic...
Decreased proportion of type I myofibers in skeletal muscle of dogs with chronic heart failure.
Authors: H NSabbah, FHansen-Smith, V GSharov, TKono, MLesch, P JGengo, R PSteffen, T BLevine, SGoldstein
Journal: Circulation (1993)

BACKGROUNDWhether biochemical and histological abnormalities of skeletal muscle (SM) develop in patients with chronic heart failure (HF) remains controversial. In the present study, dogs with chronic HF were used to examine potential alterations of SM fiber type, fiber size, number of capillaries per fiber (C/F), beta-adrenergic receptor density (Bmax), and fiber ultrastructural integrity.METHODS AND RESULTSHF was produced in 17 dogs by sequential intracoronary microembolizations. Biopsies of the lateral head of the triceps muscle were used in all studies. Type I and type II fibers were differentiated by myofibrillar ATPase (pH 9.4 or 4.2). Bmax was assessed by radioligand binding and SM ultrastructure by transmission electron microscopy. Comparisons were made with biopsies obtained from nine control dogs. The percentage of SM type I fibers was reduced in HF dogs compared with control dogs (19 +/- 2% versus 32 +/- 5%) (p < 0.001), whereas the percentage of SM type II fibers was increased (81 +/- 2% versus...