In this randomised, double-blind, placebo-controlled, 2-year multicentre study intrathecally administered natural human fibroblast interferon (IFN-B) was effective in reducing exacerbations of multiple sclerosis (MS) in patients with exacerbating/remitting disease. The mean reduction in exacerbation rate of 34 patients who received IFN-B (recipients) was significantly greater during the study than that of 35 patients who received placebo (p less than 0.04). The prestudy exacerbation rates were comparable in recipients and controls, but the rate at the end of the study was significantly lower in recipients than in controls (p less than 0.001). IFN-B was given by nine or ten lumbar punctures over the first 6 months of the study, and patient observations continued for 2 years. IFN-B was well tolerated in 95% of the recipients, and the side-effects experienced were clearly acceptable for the benefits achieved. Low doses of indomethacin reduced the toxicity of IFN-B and played an important role in successful double-blinding.

Clinical Trials as Topic↗

PubMedDate not supplied

A survey of the natural occurrence of Fusarium mycotoxins in cereals grown in New Zealand in 1986-1989.

Fusarium mycotoxins, principally trichothecenes, occurred commonly in grain from crops in the North Island of New Zealand, but were much less common and also at the much lower levels in grains from South Island regions. The principal contaminants were trichothecenes of the nivalenol (NIV) and deoxynivalenol (DON) types. Trichothecenes derived from scirpentriol and T-2 tetraol were not common. Moniliformin occurred very rarely, while zearalenone contamination was not uncommon, but the levels were generally low. Maize kernels were commonly contaminated by moderate levels of both NIV- and DON-type trichothecenes, with levels up to 3.6 mg/kg and 11.95 mg/kg respectively recorded. The occurrence of NIV-type trichothecenes as a general contaminant in the range of 0.3-0.8 mg/kg, and frequently as the main contaminant, is unusual.

Cyclobutanes↗

PubMedDate not supplied

The stability of ethyl alcohol in forensic blood specimens.

Headspace gas chromatography was used to reanalyze forensic blood specimens for ethyl alcohol content after storage at room temperature for 3.0 and 6.75 years. All samples exhibited a decline in ethanol concentration, with most losses falling within the expected 20 to 40 mg% range.

Chromatography, Gas↗

PubMedDate not supplied

A simple and compact total artificial heart for temporary use.

Thromboembolism and anatomic fit are the major issues to be addressed in the design of a heart replacement device for total circulatory support. In an attempt to overcome these problems, a simple 70 mm3 displacement pusher plate, low pressure, pneumatically driven TAH was developed for temporary use. For optimal anatomic fit, easy implantation, and better flow patterns, the 5.7 X 10.7 cm total artificial heart (1) TAH was made of two essentially flat pumps integrated into a single unit. This single package approach avoids the dead space that occurs between the two pieces of conventional TAH and thus minimizes overall volume. It was designed to be positioned in the pericardial sac in a fashion similar to the natural ventricles and, based upon previous anatomic studies, fit in the average sized adult patient. In contrast to conventional free diaphragm pumps, the diaphragms of this TAH are supported by pusher plates that have a unique guide mechanism at the center to ensure a linear-controlled diaphragm motion and consequent uniform blood flow distribution. The guide of each pusher plate nests into the other, resulting in minimal thickness of the package. By using a simple displacement transducer, reliable output monitoring, with the possibility of selection of various pumping modes and adjustment of stroke volume, is possible. The authors anticipate this efficient and practical TAH to be a suitable temporary heart replacement device.

Heart Failure↗

PubMedDate not supplied

High efficiency magnetic bearing for a rotary blood pump.

Mohawk Innovative Technology, Inc. (MiTi; Albany, NY) and the Cleveland Clinic Foundation (Cleveland, OH) have been engaged in a joint project to develop a new, high efficiency magnetic bearing for use in a rotary blood pump. Such a bearing would have some advantages with respect to permitting large, low shear clearances and avoiding crevice-like pivot interfaces and surface wear related issues. While magnetically suspended blood pumps have been demonstrated, other prototypes reported in the literature consume 5-15 W of power to energize the bearing. The MiTi bearing has been prototyped and tested. The design is a hybrid configuration, radially passive and axially active. The rotor-and-bearing system has been run in air and in blood analog solution, in all orientations. Measurements show a bearing power consumption below 0.5 W. Vibration peaked at 0.2 g in blood analog solution; frequency analysis indicated that this was primarily related to motor design features. Measured displacements from the equilibrium position were less than 0.005 cm. Based on this highly successful bearing prototype, an integrated pump/bearing system is now being developed.

Heart-Assist Devices↗

PubMedDate not supplied

Stable blood lubricated hydrodynamic journal bearing with magnetic loading.

The Cleveland Clinic Foundation's Innovative Ventricular Assist System (IVAS) is distinguished by the use of a special hydrodynamic journal bearing to support the rotating assembly of the blood pump. In a permanently implanted blood pump, this bearing's characteristics of long life and high reliability are of paramount importance. In addition, this bearing's inherent self-pumping flow and the axial through flow caused by an imposed end-to-end pressure difference provides good washing, thus guarding against deposition. The basic computer analysis and preliminary testing results of this bearing were previously presented. This article reports the ongoing studies (both analytic and in vitro tests) on this innovative bearing as a component of the IVAS in general, with particular emphasis on its stable operating characteristics and reliability. The absence of vibration attributable to hydrodynamic instabilities related to the thick fluid film are both calculated and demonstrated during testing. A stable operating center of the rotor is shown to be inherent under magnetic side loads and resulting hydrodynamic bearing forces. A low shear as a result of large fluid-film thicknesses has been calculated, and low hemolysis has been shown by in vitro testing. Several unique design features of the bearing are believed to be responsible for this high level of performance.

Heart-Assist Devices↗

PubMedDate not supplied

Numeric flow simulation for an innovative ventricular assist system secondary impeller.

The secondary impeller of the Cleveland Clinic Foundation Innovative Ventricular Assist System heart pump is designed to pump the blood from the journal bearing through the annulus back to the discharge to rejoin the main flow. It is crucial, however, that the amount of hemolysis and potential for thrombus formation is minimized. Based on our earlier computational fluid analysis of the initial design, an improved secondary impeller has been proposed. The objective of this work was to analyze the flow with the new impeller configuration by computational fluid dynamics and to find out where in the geometry hemolysis becomes high, as well as where the potential for thrombosis exists. The present work includes: 1) visualizing the 3-dimensional flow pattern in the secondary impeller cavity, 2) investigating the tip clearance effect, and 3) estimating the shear stress distribution as a measure for blood damage caused in the secondary impeller cavity.

Blood Flow Velocity↗

PubMedDate not supplied

Numeric modeling of the cardiovascular system with a left ventricular assist device.

A numeric model consisting of a lump-parameter cardiovascular system (CVS) model and a model for the Cleveland Clinic Implantable Ventricular Assist System (IVAS), a nonpulsatile rotary pump designed to augment the failing left ventricle, are described in this paper. The purposes of this study were to 1) observe the hemodynamic interactions between CVS and IVAS under various physiologic and pathophysiologic conditions running at different speeds; and 2) allow testing and optimization of various IVAS control algorithms. An existing numeric model of CVS (24 coupled differential equations, representing all cardiac chambers and systemic and pulmonary vasculature) was modified to add the IVAS pump as an auxiliary chamber between the left ventricle and aorta with pressure-flow-speed characteristics derived from in vitro testing. Simulations were conducted for ventricles with normal and abnormal systolic and diastolic dysfunction at different exercise levels with the pump running at various speeds. Computer simulations show that 1) numeric modeling is useful for predicting hemodynamic response of CVS to IVAS in various circumstances; 2) IVAS results in normalization of cardiac output, especially in failing hearts, although with reduced pulse pressure; and 3) various control algorithms allowing adaptation of IVAS to physiologic demands of CVS could be developed based on the simulation study.

Blood Pressure↗

PubMedDate not supplied

Short exposure time sensitivity of white cells to shear stress.

White cells are a critical functional element circulating in blood. This study sheared fresh whole bovine blood in stainless steel and polymeric capillary tubes of various lengths and diameters. Flow rate was constant, resulting in a range of exposure times and shear stresses. White cell count, cell integrity (trypan blue exclusion), and phagocytic index (latex bead ingestion) were assayed. It was found that cell function declined at lower stresses than cell count. White cell count was maintained at higher stress levels at the short exposure times used here compared with the published results at longer times. This study suggests that function, not count, is the critical parameter when studying shear effects on white cells, and that, like red cells, there may be an exposure time effect and that white cell function is impacted at stresses lower than are required for hemolysis.

Animals↗