ABSTRACT
We present the design and testing of a rotating device that fits within a commercial helium cryostat and is capable of providing at 4 K a fresh sample surface for subsequent shots of a 1-10 kHz amplified pulsed laser. We benchmark this rotator in a transient-absorption experiment on molecular switches. After showing that the device introduces only a small amount of additional noise, we demonstrate how the effect of signal degradation due to high fluence is completely resolved.
Subject(s)
Artifacts , Freezing , Specimen Handling/instrumentation , Spectrophotometry, Ultraviolet/instrumentation , Equipment Design , Equipment Failure Analysis , Reproducibility of Results , Sensitivity and Specificity , Specimen Handling/methods , Spectrophotometry, Ultraviolet/methods , Time FactorsABSTRACT
This study compares the effects of digoxin, placebo and ibopamine (SB-7505), the orally active 3,4-diisobutyryl ester of N-methyl-dopamine, on exercise tolerance and cardiac rhythm of 14 patients whose left ventricular heart failure (end-diastolic pressure, 26.3 +/- 5.9 mmHg; ejection fraction, 0.42 +/- 0.10%) depended on a previous myocardial infarction. Patients were admitted to the study while on chronic oral digoxin treatment (serum levels between 1.1 and 1.9 ng/ml). Placebo instead of digoxin was given for the following month. Thereafter ibopamine 50 mg t.i.d. for one month was given. A sequence of one-month treatments with digoxin, placebo and ibopamine was repeated, then ibopamine was administered continuously for the next two months. The concurrent treatment (diuretics in all patients, nitroderivates in twelve, calcium antagonists in two) remained unchanged during the observation period. Symptoms-limited exercise tests and 24-h Holter recordings were obtained at admission, at the end of each one-month treatment and at the end of the observation period. Two patients developed unstable angina without increase of serum creatine phosphokinase while on ibopamine and were withdrawn. Out of the 12 patients that concluded the trial, one required supplementary doses of diuretic at the end of the second period on placebo. The results obtained during the trial suggest that: a) therapeutic plasma levels of digoxin have no deleterious effect on cardiac rhythm nor significantly increase exercise tolerance as compared with placebo; b) diuretics and nitrates appear to sustain the clinical stability of these patients as a group.(ABSTRACT TRUNCATED AT 250 WORDS)
Subject(s)
Cardiotonic Agents/therapeutic use , Deoxyepinephrine/analogs & derivatives , Digoxin/pharmacology , Dopamine/analogs & derivatives , Heart Failure/drug therapy , Myocardial Infarction/complications , Aged , Arrhythmias, Cardiac/etiology , Arrhythmias, Cardiac/prevention & control , Cardiotonic Agents/adverse effects , Deoxyepinephrine/adverse effects , Deoxyepinephrine/blood , Deoxyepinephrine/pharmacology , Digoxin/adverse effects , Digoxin/blood , Female , Heart Failure/etiology , Heart Failure/physiopathology , Heart Rate/drug effects , Humans , Male , Middle Aged , Physical ExertionABSTRACT
Antiarrhythmic effectiveness of N-methyl-N-(beta-hydroxyethyl) guanidine O-phosphate (creatinol O-phosphate, COP) has been investigated in 10 patients with ischemic heart disease and frequent premature ventricular contractions (PVCs). Each patient received a random succession of treatment with the drug (1020 mg) and with a reference substance (solvent of COP) both administered i.m. twice a day over a 3-day period. In each patient a Holter ECG was recorded in the basal state and during the last 24 h of each treatment. Heart rate, PQ and QTc showed no changes. On the contrary, PVCs were significantly lower (P less than 0.01) with COP than with the reference substance. The drug showed a prevailing effect during daytime. Results are discussed in view of experimental observations suggesting that COP has a "membrane effect".
