PubMed Health⌕ Search

Biomedical subjects

W M Phillips

Publications and source records attributed to W M Phillips.

At least 19 recordsLinked to original sources
PubMed1991

Infrared spectroscopic studies on the phosphatidylserine bilayer interacting with calcium ion: effect of cholesterol.

Fourier transform infrared (IR) spectroscopic studies of phosphatidylserine/cholesterol/Ca2+ complexes are reported using the synthetic phosphatidylserines (PS) 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), and 1,2-dimyristoyl-sn-glycero-3-phospho-L-serine (DMPS). IR spectra reveal that cholesterol does not significantly alter the binding nature of Ca2+ to PS molecules; Ca2+ binds to the phosphate ester group of PS in the presence of cholesterol up to 50 mol% as in the case of pure PS bilayers. However, the IR data indicate that the presence of cholesterol induces disorder of the acyl chain packing, increases the degree of immobilization of the interfacial and polar regions, and increases the degree of dehydration of the PS/Ca2+ complexes.

Calcium↗
PubMed1990

No safe place: parental alcoholism and adolescent suicide.

A child growing up in an alcoholic home develops either little self-consolidation (I-ness) and efficacy (I can) or a distorted self (I am insignificant). This results in a desperate search for a soothing-object (We-ness). The sadomasochistic behaviors, which a youth witnesses and is subjected to, become internalized as survival skills, but ultimately fail. These factors set the stage for a destructive modus operandi. When there is peer group attachment pressure, this teen does not find security when questioning, "Who am I?" because there is no "I" and no "We". Instead, this adolescent experiences fear, anxiety, and range, and wonders, "What's going to happen to me?" This propels the youth into frantic behaviors that are meant to confirm a sense of "We-ness" and competence. The result, however, is greater frustration and a mirroring of the opposite. Also, since there is a diminutive capacity for trust and an exiguous chance to reach out or respond to significant others, external soothingness becomes unobtainable. When the adolescent is confronted with aloneness, helplessness, and hopelessness, desperation results and a search for a safe place ensues. Suicide holds such an illusion. It is the embodiment of sadomasochism and permits the cognition "I am capable." A case study illustrates the problems.

Adolescent↗
PubMed1989

Effect of tilting disk, heart valve orientation on flow through a curved aortic model.

The influence of tilting disk valve orientation on pulsatile flow through a curved tube model of the human aorta was studied. Simultaneous, two-component laser Doppler velocimeter measurements were made in a tube having a 22 mm diameter and 41 mm radius of curvature which simulated the average dimensions of the adult aorta. The blood analog fluid had a viscosity of 3.0 cp and matched the refractive index of the glass model aorta. Results at mid-arch showed low turbulence levels in early systole and no influence of valve orientation. During mid-systole, fluid from the ventricle reached mid-arch exhibiting strong influence of valve orientation and increased turbulence levels. With the major orifice of the valve adjacent to the inner curved wall, the peak turbulent shear stress was 307 dynes/cm2 at mid-arch during mid-systole. When the major orifice was rotated 180 degrees, the peak value was reduced to 91 dynes/cm2 at the same location and time. At the exit of the curved section, the flow was independent of the valve orientation and the turbulent shear the flow was independent of the value orientation and the turbulent shear stress levels were an order of magnitude lower than the peak value at the inlet. This study demonstrated that orienting the major orifice of a tilting disk valve adjacent to the outer curved wall minimized turbulent shear stress levels.

Aorta↗
PubMed1988

Influence of cardiac flow rate on turbulent shear stress from a prosthetic heart valve.

Elevated turbulent shear stresses associated with sufficient exposure times are potentially damaging to blood constituents. Since these conditions can be induced by mechanical heart valves, the objectives of this study were to locate the maximum turbulent shear stress in both space and time and to determine how the maximum turbulent shear stress depends on the cardiac flow rate in a pulsatile flow downstream of a tilting disk valve. Two-component, simultaneous, correlated laser velocimeter measurements were recorded at four different axial locations and three different flow rates in a straight tube model of the aorta. All velocity data were ensemble averaged within a 15 ms time window located at approximately peak systolic flow over more than 300 cycles. Shear stresses as high as 992 dynes/cm2 were found 0.92 tube diameters downstream of the monostrut, disk valve. The maximum turbulent shear stress was found to scale with flow rate to the 0.72 power. A repeatable starting vortex was shed from the disk at the beginning of each cycle.

Blood Flow Velocity↗
PubMed1986

Two-component laser velocimeter measurements downstream of heart valve prostheses in pulsatile flow.

Elevated turbulent shear stresses resulting from disturbed blood flow through prosthetic heart valves can cause damage to red blood cells and platelets. The purpose of this study was to measure the turbulent shear stresses occurring downstream of aortic prosthetic valves during in-vitro pulsatile flow. By matching the indices of refraction of the blood analog fluid and model aorta, correlated, simultaneous two-component laser velocimeter measurements of the axial and radial velocity components were made immediately downstream of two aortic prosthetic valves. Velocity data were ensemble averaged over 200 or more cycles for a 15-ms window opened at peak systolic flow. The systolic duration for cardiac flows of 8.4 L/min was 200 ms. Ensemble-averaged total shear stress levels of 2820 dynes/cm2 and 2070 dynes/cm2 were found downstream of a trileaflet valve and a tilting disk valve, respectively. These shear stress levels decreased with axial distance downstream much faster for the tilting disk valve than for the trileaflet valve.

Blood Flow Velocity↗
PubMed1979

Laser Doppler anemometer studies in unsteady ventricular flows.

The laser Doppler technique was employed to obtain intraventricular velocity distributions on the basis of in vivo confirmation of previous in vitro flow visualization predictions. The quasi-steady assumption required for quantification of flow visualization results is unsatisfactory in regions of high acceleration and fluctuating velocities are unavailable via such techniques. Mean and fluctuating velocity profiles were obtained in a pneumatically driven prosthetic ventricle with the laser Doppler anemometer and stress levels estimated. The preliminary data presented here illustrates that the technique can be applied to such flows. The measurement and data reduction schemes are applicable to a wide range of simulated cardiovascular flows. The particular application to prosthetic ventricle design should minimize the number of in vivo experiments required to develop a satisfactory blood pump and aid in tailoring pump actuation protocols for minimum thromboembolic complications.

Blood Flow Velocity↗
PubMed1979

Total artificial heart implantation in calves with pump on an angled port design.

The APP was employed in our 21st TAH calf and has now been implanted in a total of 11 animals. The APP has a dynamic stroke volume of 105 ml, an ejection fraction of 75%, and a peak flow of 14 L/min. The TAH features 2 APPs which have polysulfone cases and contain smooth, seam-free polyurethane sacs. Concavoconvex Bjork-Shiley valves are used. The pumps are pneumatically driven but may be easily converted to pusher-plate drive. A pneumatic drive console and an automatic control unit complete the system. The automatic control unit permits independent control of the right and left hearts as a function of left atrial and aortic pressure respectively. The average survival of the APP TAH calves has been 65 days. Hematologic study has revealed basically normal results with minimal elevation of serum hemoglobin and lactic acid dehydrogenase (LDH), indicative of a low level of hemolysis. Elelvation of central venous pressure (CVP) and total blood volume continue to be a problem with some TAH calves but not all. The APP has led to a dramatic increase in duration of survival and decrease in thromboembolism.

Animals↗
PubMed1979

A two and one half year clinical experience with a mechanical left ventricular assist pump in the treatment of profound postoperative heart failure.

A sac-type paracorporeal left ventricular assist pump was implanted in 9 patients suffering from profound left ventricular failure following open heart surgery. Two patients had good recovery of left ventricular function and were weaned from assist. One survived 14 months postoperatively. Primary causes of death among the remaining patients were (1) primary right ventricular failure, (2) assist pump inlet cannula obstruction and (3) excessive bleeding. The strategies developed or proposed to deal with these problems include, respectively: (1) biventricular assist for patients with concomitant right ventricular failure; (2) cannulation of the left atrium to avoid inlet cannula obstruction by the left ventricular wall and intraventricular septum; (3) more rapid selection of left assist candidates and more rapid implantation techniques to reduce the coagulopathy associated with prolonged cardiopulmonary bypass, and an effective autotransfusion system to augment blood replacement.

Adult↗
PubMed1978

Determining arterial pressure, left atrial pressure and cardiac output from the left pneumatic drive line of the total artificial heart.

These data presented here demonstrate how careful analysis of mock loop testing can lead to useful measurements for long-term calf experiments. The accuracy of the data rae primarily dependent upon a valid circulatory system analog and good experimental technique. These methods of determining arterial pressure, left atrial pressure and cardiac output have allowed us to obtain recordds of these important parameters for periods as long as 100 days in calves with total artificial heart implantation. These methods have also enabled us to automatically control the artifical heart under conditions of rest, exercise and pharmacologic treatment with the use of only one external pneumatic drive line pressure transducer.

Animals↗
PubMed1976

Similarity between complexity on Role Construct Repertory Technique and articulation on Draw-A-Person test for patients and non-patients.

In an investigation of the underlying unity of the articulation of human figure drawings and personal construct complexity, moderate correlations were found, but in opposite directions, for inpatient and non-patient groups. For inpatients, greater construct complexity was associated with less sophisticated drawings. For non-patients, greater construct complexity was correlated with more sophisticated human figures. Mean and range differences in complexity and articulation scores between the two groups suggested that the higher complexity scores of the patient group indicated a loss of construct coordination, rather than greater articulation and organization of self and interpersonal experience.

Adolescent↗
PubMed1976

A pressure-measuring system for long-term in vivo pressure measurements.

A new balloon-tipped catheter has been developed for the purpose of making long-term vivo intravascular pressure measurements. Among its advantages are its ability to electrically isolate the subject from the pressure transducer and be rebalanced and calibrated while in situ. Experimental results in calves indicate that the system provides a very reliable means of calibrating implanted catheter tip pressure transducers in situ and can be used as the primary long-term pressure measuring device when high frequency response is not required.

Animals↗
PubMed1976

A comparison of three ventricles used for left ventricular bypass in the calf.

Long-term synchronized left ventricular bypass has been performed in calves using pneumatically powered pumps having a smooth lining fabricated of segmented polyurethane. Three different pump designs have been employed: a) sac pump, b) longitudinal tethered sac pump, and c) transverse tethered sac pump. Sizeable thrombi occurred in the apex of the sac and longitudinal tethered sac pumps. In the transverse tethered sac pumps, a considerably smaller thrombus was seen only at the flexion point on the inlet side of the pump. Thrombi occurred in areas of low flow velocity and were not prevented by anticoagulation or surface coating techniques. This study indicates the importance of ventricle design in the development of thrombus free pumps and suggests modifications to the present pumps to reduce or eliminate thrombus formation.

Animals↗