The precipitation of enzymes from cell extracts of Saccharomyces cerevisiae by polyethyleneglycol.

The equilibrium precipitation by polyethyleneglycol of alcohol dehydrogenase, fumarase and invertase from Saccharomyces cerivisiae has been studied. The precipitation can often be represented by a simple linear equation analogous to Cohn's equation for salting-out: log S = X-a x C where S is the protein solubility and C the concentration of polymer, X and a are constants. A more complex form of the equation log S + fS = X-a x C where f is a protein self-interaction coefficient, is sometimes necessary, particularly at high protein concentrations and at pH values distant from the isoelectric point. Protein solubility with respect to polyethyleneglycol is influenced by temperature and ionic strength and particularly by pH and protein concentration. Different results were obtained by discrete and sequential addition of polyethyleneglycol. Effective fractional separation of the enzymes is restricted to protein concentrations below about 10 mg/ml.

Interactions between electronic article surveillance systems and implantable cardioverter-defibrillators.

BACKGROUND: In patients with implantable cardioverter-defibrillators (ICDs). inappropriate shocks have been reported with exposure to electronic article surveillance systems. The risk to patients with ICDs of walking through or lingering near surveillance systems requires further investigation. METHODS AND RESULTS: We evaluated the response in ICD function in 170 subjects during a 10- to 15-second midgate walk-through of and during extreme (2 minutes within 6 in of the gate) exposure to 3 common article surveillance systems. Complete testing was done in 169 subjects. During a 10- to 15-second (very slow) walk-through of the 3 surveillance systems, no interactions were observed that would negatively affect ICD function. During extreme exposure (169 subjects) and during extreme exposure and pacing via the ICD (126 subjects), interactions between the ICD and the article surveillance systems were observed in 19 subjects. In 7 subjects, this interaction was clinically relevant and would have likely (3 subjects) and possibly (4 subjects) resulted in ICD shocks. In 12 subjects, the interaction was minor. CONCLUSIONS: It is safe for a patient with an ICD to walk through electronic article surveillance systems. Lingering in a surveillance system may result in an inappropriate ICD shock.

Changes in factor VIII complex activities during the production of a clinical intermediate purity factor VIII concentrate.

Samples taken at various stages of preparation of intermediate purity factor VIII concentrate were assayed for factor VIII coagulant activity (VIII:C), factor VIII coagulant antigen (VIIIC:Ag) and factor VIII related antigen (VIIIR:Ag). The antigen results were used to assess mechanical loss during fractionation as these markers are relatively stable. In contrast VIII:C is sensitive to both mechanical and inactivation losses. The major loss of factor VIII occurred during the cryoprecipitation and extraction step and was due to both mechanical loss and inactivation. Losses before and after this step were largely due to inactivation of the factor VIII. Assay of VIIIR:Ag in concentrates presented problems and a modified technique is suggested.

Atrial induction of ventricular tachycardia: reentry versus triggered automaticity.

Atrial stimulation induced a sustained ventricular tachycardia in two patients with mitral valve prolapse and in one patient who had mild hypertension without cardiac abnormalities. Exercise-induced sinus tachycardia also started the ventricular tachycardia in one patient. Evidence is presented to suggest that the mechanism of ventricular tachycardia in one patient was reentrant excitation and in another patient triggered automaticity. It is likely that the origin of the ventricular tachycardia was confined to a relatively protected small area near the posteroinferior portion of the left ventricle and was not due to macroreentry.

The viral safety of intravenous immunoglobulin.

Human immunoglobulin for intravenous (IV) use has an established safety record with regard to transmission of hepatitis B virus. The bulk of available evidence also suggests that the human immunodeficiency virus (HIV) is not transmitted by IV immunoglobulin. There has been one report, however, of isolation of HIV from two patients with hypogammaglobulinaemia who had been treated with several immunoglobulin products. Certain IV immunoglobulin products have transmitted non-A, non-B (NANB) hepatitis but careful clinical assessment of recipients of other products suggests that non-infective preparations can be made. Interpretation of available data most likely to be correct is that contamination with NANB is reduced but not eliminated by cold-ethanol fractionation and that the use of further virucidal procedures in the finishing of immunoglobulin products will confer a higher degree of safety.

Effect of weight loss on inflammatory and endothelial markers and FMD using two low-fat diets.

OBJECTIVE: Cardiovascular disease is strongly associated with obesity and there is evidence that weight loss has positive effects on cardiovascular disease risk. The aims of this study were to compare meal replacements (MR) with a conventional low-fat diet as weight loss strategies and to examine the effect of weight loss on flow-mediated dilatation (FMD) and other markers of endothelial function in overweight Australians with raised triglycerides (TG) (> 2 mmol/l). RESEARCH METHODS: Subjects matched for age, gender, fasting plasma TG and body mass index were randomized to two low- fat high- carbohydrate weight loss strategies (both < 6000 kJ), one using MR and the other a structured eating plan, control (C). Subjects followed both diets for 3 months. In total, 55 subjects completed the study. FMD, pulse wave velocity and blood pressure (BP) were measured at baseline and at 3 months, as were fasting blood samples for lipids, glucose, insulin, C reactive protein (CRP) and endothelium-derived factors. RESULTS: Mean weight loss was 6.3 +/- 3.7 kg (6.0 +/- 4.2 vs 6.63 +/- 3.35 kg, MR vs C) with no difference between diet groups. TG, insulin, CRP, plasminogen activator inhibitor 1 (PAI-1) and soluble intracellular adhesion molecule-1 (sICAM1) fell after weight loss, but FMD did not change. Systolic BP fell by 8 mmHg and pulse wave velocity improved. DISCUSSION: In subjects with elevated TG, weight loss resulted in significant improvements in cardiovascular risk markers, particularly endothelium-derived factors (PAI-1 and sICAM1). However, FMD did not improve with weight loss.

Assessment of the potential of plasma fractionation processes to remove causative agents of transmissible spongiform encephalopathy.

Although there is no evidence that classical CJD (cCJD) can be transmitted by human blood or blood products in clinical practice, uncertainties surrounding new variant CJD (nvCJD) have led to the safety of plasma products derived from UK donors being questioned. To better define whether or not there is a risk of nvCJD being transmitted it is necessary to determine how the causative agent would partition across the separations processes used in the preparation of plasma products. The abnormal prion protein which is associated with transmissible spongiform encephalopathies (TSEs), such as CJD, has a low solubility, a high tendency to form aggregates and adheres to surfaces readily. If the physicochemical properties of the agent of nvCJD are similar to those of abnormal prion protein then nvCJD may be removed by precipitation and adsorption technologies used in plasma fractionation. Available data on the removal of TSE agents by such bioprocess technologies have been used to estimate the potential degree of reduction expected from each step in the plasma fractionation processes used by the SNBTS. The overall process reduction factors estimated are: 10(13) (albumin). 10(9) (immunoglobulins), 10(7) (factor IX, thrombin), 10(5) (fibrinogen), 10(4) (factor VIII) and 10(3) (factor II, IX and X); however, it will be necessary to establish the accuracy of these estimates by practical validation studies.

Prions and blood products.

The transmission of Creutzfeldt-Jakob disease (CJD) by human pituitary-derived growth hormone has led to concerns that blood products might also provide a route for the iatrogenic transmission of CJD. A number of actions have been implemented by regulatory authorities to address such concerns, and numerous studies have been undertaken to determine whether or not there is a risk of CJD being transmitted in this manner. To date, no excess risk has been identified, leading to a growing consensus that there is little or no risk of long established forms of CJD being transmitted to recipients of blood products. This opinion does not extend to new variant CJD (vCJD) which is found predominantly in the UK and is believed to have resulted from the transmission of bovine spongiform encephalopathy (BSE) to humans. Unlike that of CJD, the prevalence of vCJD is not known. In addition, the detection of abnormal prion protein in the tonsils of vCJD-infected individuals has led to speculation that blood infectivity may be greater than in patients with CJD. A number of precautionary measures have been taken to address the possibility that vCJD may be transmissible by blood products; however, further scientific advances are needed to enable this risk to be defined. A suitable screening test is required to identify any infected blood donors, particularly where cellular blood components are being derived from populations believed to be at risk from BSE infection. Recent experimental data suggest that process operations used in the manufacture of plasma products may be capable of removing prion agents to a significant extent. However, further work is required to confirm these observations and to determine whether or not all potential vCJD infectivity would be removed by these means.

Improvement in separation characteristics of protein precipitates by acoustic conditioning.

The effect of acoustic conditioning on the particle size distribution of isoelectric and calcium-ion-precipitated soya protein has been examined in low-residence-time chambers. In a previous study a beat frequency of 5 Hz obtained using a dual-source system of opposing vibrators was determined as giving optimal improvement in particle-settling characteristics for isoelectric soya protein precipitate. In this study the effect of amplitude of vibration, a measure of acoustic power input, and residence time of acoustic conditioning has been examined. Acoustic power input changed the flow pattern in the conditioning chamber from laminar streamline flow to a well-mixed, turbulent pattern. Such a mixing effect promoted the rapid aggregation of fine particles, a process that was modeled on the basis of orthokinetically controlled collisions. The rate of removal of fine particles due to acoustic conditioning was shown to be proportional to a mixing effect that was related to the acoustic power dissipated per unit volume. The consequences of fine-particle aggregation on the centrifugal recovery of the precipitate are discussed.

Effects of aprindine HCL on cardiac tissues.

The effects of aprindine HCL on cardiac tissues were studied in anesthetized, open-chest dogs pretreated with atropine (0.8 mg/kg) and propranolol (1.0 mg/kg). Aprindine (10(-5)-10(-3) g/ml), injected into the sinus node artery, decreased the spontaneous sinus rate; when injected into the atrioventricular nodal artery, aprindine (10(-4) g/ml) prolonged the conduction time and functional refractory period of the atrioventricular node. Intravenous administration of aprindine (1.4, 2.8 and 4.2 mg/kg cumulative dose) prolonged atrial and ventricular conduction time and prolonged the effective refractory period of both tissues. The results from this study indicate that aprindine has a negative dromotropic effect on all cardiac tissue.

The kinetics of protein salting-out: precipitation of yeast enzymes by ammonium sulfate.

Protein solubility can be adequately represented by the classical Cohn equation for the salting-out of alcohol dehydrogenase and fumarase from clarified yeast homogenate with ammonium sulfate. However, the constant beta in this equation is a function of the contacting procedure employed. The kinetics of continuous salting-out were similar for alcohol dehydrogenase and fumarase. The overall rate equation for precipitation had a variable order which was high initially, up to 3.1, but approached unity on completion of precipitation. This was followed by a partial resolution stage which was first order with respect to the concentration driving force. Precipitate particle size was estimated as 0.5 to 5 mum with continuous flow precipitation producing the largest particles.

Accelerated ventricular escapes induced in the intact dog by barium, strontium and calcium.

Accellerated ventricular escapes (AVE) were produced with infusion of BaCl2, SrCl2 and CaCl2. AVE demonstrated overdrive acceleration rather than overdrive suppression, i.e., faster pacing rates caused shorter escape intervals. BaCl2 (mean 20.2 mumol/kg) produced AVE in 18 of 23 dogs and a decrease in mean serum potassium (K+). SrCl2 alone (mean 2494 mumol/kg) did not produce AVE in 5 dogs and K+ was unchanged. When insulin and glucose were infused to lower K+ and SrCl2 was infused 30 minutes later, AVE was demonstrated in 7 of 10 dogs. CaCl2 alone (mean 1628 mumol/kg) produced AVE in 3 of 5 dogs and CaCl2 (mean 1733 mumol/kg) infused 30 minutes after insulin and glucose produced AVE in 4 of 4 dogs. This study demonstrates that AVE previously produced with cardiac glycosides can also be induced by infusion of barium, strontium and calcium.

Subxiphoid approach for implantable cardioverter defibrillator in patients with previous coronary bypass surgery.

From February 1988 until August 1991, 28 patients with prior coronary artery bypass grafting (CABG) received implantable cardioverter defibrillator (ICD) therapy via a subxiphoid approach. Only one patient required conversion to a median sternotomy incision. The mean defibrillation threshold was 11.9 +/- 4.4 J. The mean R wave was 8.2 +/- 3.7 mV. One perioperative death occurred due to heart failure (mortality rate 1/28 [3.50%]). No patient required reexploration for bleeding. The subxiphoid method for ICD electrode implantation is safe and reliable in patients with prior CABG surgery.

Intracoronary infusion of dilute ethanol for control of ventricular rate in patients with atrial fibrillation.

The effects of selective infusion of 25% ethanol into the AV nodal artery was assessed in 11 patients with atrial fibrillation and uncontrollably rapid ventricular response rates. The primary study objective was to achieve permanent modification of AV nodal function and control ventricular rate without drug therapy and without causing permanent complete AV block. "Clinical success" was defined as drug-free rate control by either AV nodal modification or the production of complete AV block. Selective catheterization and ethanol infusion into the AV nodal artery could be performed in nine patients. Intracoronary ethanol infusion acutely caused second- or third-degree AV nodal block in seven patients and an increase in AV nodal refractory period and Wenckebach cycle length in two patients. Acute occlusion of the AV nodal artery or infarction of nontarget myocardium was not observed. During follow-up of 22.2 +/- 2.2 months the primary study objective was attained in only four of nine patients treated, yielding an efficacy of 44%. However, the "clinical success" rate was 78%. The acute effects of ethanol on AV conduction did not predict the chronic effects. Selective intracoronary infusion of dilute ethanol to control the ventricular rate in atrial fibrillation should be considered when radiofrequency ablation has been unsuccessful. This method of chemical ablation is as effective and probably safer than rapid administration of 96% ethanol.

Ventricular tachycardia and ventricular fibrillation in a young population.

In this study, we describe the findings in 18 young patients (age range 4 days to 24 years, mean 16.6 years) who had ventricular tachycardia and/or ventricular fibrillation and were followed for 4--70 months (mean 22.4 months). Patients had a variety of problems associated with their arrhythmia, including mitral valve prolapse, cardiomyopathy, myocarditis, prolonged QT syndrome and hypokalemia. Six patients had no clinically recognizable cardiac abnormality. The ventricular tachycardia showed a left bundle branch block contour in 10 of 17 patients, right bundle branch block in four, was multiform in two and had an indeterminate contour in one. Sustained ventricular tachycardia was initiated and terminated reproducibly by atrial and ventricular stimulation in three of seven patients who did not have spontaneous episodes of ventricular tachycardia during the electrophysiologic study. In one other patient, short bursts of ventricular tachycardia were induced. Patients who had ventricular fibrillation, those who died, and those who are still symptomatic with poorly controlled ventricular arrhythmias had significant heart disease. In one patient, a ventricular tachyarrhythmia that had required more than 100 electrical cardioversions spontaneously disappeared after requiring 1 year of antiarrhythmic therapy.

Acute and chronic haemodynamic effects of prazosin in left ventricular failure.

We evaluated the acute and chronic effects of prazosin treatment in 11 patients with chronic congestive heart failure, NYHA functional class III and IV. Before treatment mean arterial pressure averaged 100 +/- 15 mmHg, left ventricular filling pressure 29 +/- 11 mmHg, and systemic vascular resistance 2372 +/- 1121 dynes s cm-5. Prazosin administration resulted in haemodynamic improvement in all but one patient with significant lowering of the mean arterial pressure, left ventricular filling pressure, and systemic vascular resistance. Nine patients completed a 10-week course of ambulatory treatment. Five patients remained improved while four developed significant fluid retention; two of these had transient exacerbation of congestive heart failure. This was controlled by increasing diuretic and/or prazosin treatment. After 10 weeks all nine patients had advanced to NYHA functional class II. Repeat haemodynamic measurements disclosed complete haemodynamic tolerance in one patient while three other patients showed partial tolerance with a lower cardiac output (CO) response to prazosin. The nine patients, however, still showed significant lowering of the mean arterial pressure, left ventricular filling pressure, as well as the systemic vascular resistance. Though pharmacodynamic tolerance was noted in four out of nine patients, beneficial clinical and haemodynamic effects could be demonstrated after 10 weeks of prazosin treatment in most patients. Further evaluation of the long-term effects of prazosin in chronic congestive heart failure is warranted.