Surface antigens on Schistosoma mansoni. II. Adsorption of a Forssman-like host antigen by schistosomula.
Explore the source record for details and available documents.
Adsorption↗
Biomedical subjects
D A Dean
Publications and source records attributed to D A Dean.
The role of ATP as the energy source for maltose transport in Escherichia coli.
Explore the source record for details and available documents.
Adenosine Triphosphate↗
Geometry and temperature dependence of conductance ventriculography.
The conductance catheter allows continuous monitoring of ventricular volume in vivo, but shape and temperature dependence have not been defined. Accordingly, an in vitro experiment was performed to assess the potential utility of conductance for volume measurement during hypothermia and in asymmetric chambers resembling the right ventricle. A 5 Fr conductance catheter was placed inside an ellipsoidal latex balloon, and known volumes of normal saline were infused, while conductance volumes were measured. The geometry of the right ventricle was then approximated by compressing the balloon in a mandrel constructed of two hemi-cylinders. Measurements were repeated in this geometry. Temperature was varied at volumes of 90 ml and 120 ml in an ellipsoidal balloon, and conductance was measured. Conductance volumes were plotted versus known volumes and regression analysis was applied. Compared with the line of identity, there was no statistical difference between slopes of left ventricular geometry and RV geometry, but conductance was highly dependent upon temperature. This was reflected in rho, the resistivity of saline. Rho varied from 80 to 51 (omega-cm) while temperature varied from 8 to 38 degrees C (p < 0.01). These observations suggest that conductance may be useful for measuring right as well as left ventricular volumes. During changes in blood temperature, multiple measurements of rho, in appropriately drawn blood samples, are necessary to maintain accuracy.
Animals↗
Validation study of a new transit time ultrasonic flow probe for continuous great vessel measurements.
Continuous measurement of cardiac output is important during experimental and clinical cardiac surgery as an indicator of ventricular function. Previous flow probes underestimated flow secondary to position and flow (S-series probes; Transonic Systems, Inc., Ithaca, NY), required frequent calibrations (electromagnetic), and were cumbersome to use. The new A-series probe (ASP) by Transonic Systems, Inc., uses a new X method of ultrasonic illumination insensitive to perturbations in flow. The ASPs were found to be accurate during in vitro studies, but have not been validated in vivo. Six anesthetized pigs were instrumented for right atrium to left atrium bypass, and ASPs were placed on the ascending aorta and pulmonary artery. Baseline measurements included aortic (Ao) and pulmonic flow (P), and thermodilution (Td) cardiac output. Animals then were placed on right heart bypass, and flow was randomly varied from 1 to 6 L/min, and Ao flow was recorded. In addition, ASPs were rotated and their direction reversed. After data collection, the occlusive roller pump (RP) was calibrated using a timed collection method. Calibrated RP flows were plotted versus ASP flows, and regression was applied. There was no difference between mean Ao, P, and Td cardiac outputs at baseline. In addition, changes in position and direction of the probe did not affect measurement of flow. The ASPs showed a highly linear correlation with RP ([r = 0.98, p < 0.01] ASP[L/min] = 0.98 RP-0.032). During laminar flow states, ASPs are accurate and insensitive to position on the great vessels.
Animals↗
Validation of a novel ultrasound dilution method to measure cardiac output during hemodialysis.
A method to measure cardiac output (CO) based on ultrasound velocity dilution during hemodialysis was validated in an animal model against direct measurement using a transit time technique and a calibrated pump. In two anesthetized pigs, a 20 mm transit time ultrasound flow probe was placed on the ascending aorta to measure CO, and the right femoral artery and vein were cannulated for hemodialysis access. The dual sensor HD01 Hemodialysis Monitor was positioned on the arterial and venous tubing lines for measurement of cardiac output by ultrasound velocity dilution (COUD) by intravenous injections of 10-20 ml isotonic saline at 37 degrees C. COUD (n = 29) was compared with CO from the transit time flow probe (COT). During the second part of the experiment, the animal was placed on right atrial to left atrial bypass using a calibrated roller pump. The COUD (n = 9) was compared with cardiac output as measured by pump flow (COP). A linear relationship was observed between COUD and COT (COUD) = 0.948 x COT + 0.086 L/min, r = 0.95), and between COUD and COP (COUD = 1.06 x COP-0.327 L/min, r = 0.99). Thus, cardiac output measured by ultrasound velocity dilution during hemodialysis is in good agreement with well established, but invasive, transit time and pump standards.
Animals↗
Conductance artifacts in a novel in vitro model of ventriculothoracic electrical coupling.
The utility of open chest conductance (COND) ventriculography is limited by artifacts altering the relationship between COND and left ventricular (LV) volume. Pressure-COND loops often lean to the left during LV volume reduction by caval occlusion. Time varying alterations in the pericardial-LV contact area affect electrical coupling in the open chest during the cardiac cycle, producing COND artifacts. In this study, an open-mediastinum model was constructed. Components represented the LV, blood, pericardium, and thoracic contents. Varying ventriculothoracic coupling was simulated by changing the volume of pericardial saline (0, 30, 60 ml). Raw dual field COND was repeatedly (n = 20) compared with volumes of normal saline from 60 to 120 ml at 5 ml intervals. Groups were compared by linear regression and repeated measures ANOVA. Artifacts significantly (p < 0.01) altered parallel COND, indicated by the y-intercept, with the exception of 0 versus 30 ml. The slope constant also changed significantly, with the exception of 30 versus 60 ml. These results suggest that variable pericardial-LV contact can cause time varying artifacts in COND in the open chest. Therefore, posterior insulation may reduce artifacts in COND ventriculography and should be tested for this effect.
Analysis of Variance↗
Gene transfer to intact mesenteric arteries by electroporation.
The purpose of the present study was to develop a rapid, reproducible method of nonviral gene transfer to the intact vasculature. Male Sprague-Dawley rats were anesthetized, a midline abdominal incision was made and segmental branches of the superior mesenteric artery were dissected free of surrounding mesentery. A specially designed electroporation probe was placed around the neurovascular bundle and the electroporation chamber filled with a solution containing the firefly luciferase expressing plasmid (pCMV-Lux-DTS) or the green fluorescent protein expressing plasmid (pEGFP-N1). Vessels were electroporated with eight 10-ms pulses of 200 V/cm. Sixty seconds after electroporation, the DNA solution was removed, the intestine returned to the abdomen and the abdominal wall closed with suture and metal wound clips. Six hours to 5 days later, rats were sacrificed and electroporated vessels were recovered. Luciferase activity of the blood vessels was monitored. Gene expression was detected as early as 6 h postelectroporation, peaked at 1-3 days with levels up to 1 ng of reporter gene product per vessel segment and returned towards baseline by day 5. Histological analysis of blood vessel segments revealed green fluorescent protein-positive cells throughout the thickness of the vessel wall (endothelial cells to adventitia). Responses of electroporated vessels to vasoconstricting stimuli were indistinguishable from those of control vessels at either 2 or 40 days posttreatment. The results of this study provide evidence that electroporation is an effective means for introducing naked DNA into the blood vessel wall and form the basis for future studies on targeted gene therapy to the intact vasculature.
Animals↗
Electrical isolation of the heart. Stabilizing parallel conductance for left ventricular volume measurement.
Modern indices of left ventricular function require accurate measurement of left ventricular volume (LVV). Although conductance catheter (COND) measurements of LVV have been found to be reproducible under steady state conditions in closed chest animals, after median sternotomy, measurements of LVV are subject to exaggerated variation in parallel conductance (alpha Vc) outside of the left ventricle. Current calibration methods for measuring alpha Vc include hypertonic saline injection and quantitative two dimensional echocardiography. Unfortunately, these methods are hampered by imprecision, since frequent changes in alpha Vc in the open chest make recalibration impractical. Accordingly, a latex wrap technique was developed to insulate the left ventricle from extracardiac sources of alpha Vc in the open chest. Anesthetized pigs (n = 5) underwent a median sternotomy with insertion of a 6 French COND-micromanometer combination catheter into the left ventricle. Three conditions were tested: 1) unaltered; 2) metallic retractor outside of the pericardium (metal); and 3) latex wrap between the metal and pericardium. Pressure/COND loops showed that the insulator improved the shape of the loops and decreased alpha Vc, as measured by an echo-area/COND relationship, whereas metal increased alpha Vc and produced artifacts in the loops. In conclusion, electrical isolation eliminates distortion of pressure/COND loops related to extracardiac sources of alpha Vc, therefore allowing for accurate COND measurements in the open chest.
Animals↗