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Biomedical subjects

W S Pierce

Publications and source records attributed to W S Pierce.

At least 91 records · Page 5Linked to original sources
PubMed1983

Osmoregulation and membrane-mediated responses to altered water potential in plant cells.

Plant cells respond to short-term stress dehydration by modification of internal psi pi such that an inward gradient of psi w is maintained. In response to lowered psi w, increases in internal psi pi are created by alteration of cell inorganic ions and small organic solute content. Passive movement of water follows, changing cell hydration and forcing the plasma membrane against the elastic cell wall. The stretched cell wall presses against the cell contents, creating a hydrostatic pressure, psi p, which tends to force water out of the cell. The resulting hydrostatic pressure eventually comes into equilibrium with forces bringing water into the cell, largely psi pi, and the net flow of water ceases. The mechanism for sensing cell psi w changes is unknown but the initial event must be physical, not biochemical. The method of translation of such physical events into biochemical actions is also unknown but the Zimmermann model provides a means of signal transduction and amplification, through the alteration of membrane parameters, which could account for the observed changes. As for animal cells, cell levels of Ca2+ are important for their regulation of membrane Pj in these responses but unlike osmoregulation in higher animals, the involvement of plant hormones in these responses have not been clearly established. However, the important role of plant cell limiting membranes in plant cell osmoregulation responses seems obvious.

Adaptation, Physiological↗
PubMed1983

Survival and complications following ventricular assist pumping for cardiogenic shock.

Thirty patients (pts) have undergone ventricular assist pumping for up to 25.4 days (mean 6.8 days). Twenty-eight pts could not be weaned from cardiopulmonary bypass (CPB) after open heart operations and two pts sustained myocardial infarctions (MI), with cardiogenic shock unresponsive to medical therapy previous to surgery. Twenty-two pts required left ventricular assistance (LVA); 55% (12/22) were weaned from the pump and 32% (7/22) survived. Two pts required right ventricular assistance (RVA); both were weaned from the pump and survived. Six pts required right and left ventricular assistance (BVA) and none survived. Postoperative survival for program years 1976 through 1979 (14 pts) was 14% (2/14). Postoperative survival for program years 1980 through 1982 (16 pts) was 44% (7/16), reflecting improved pump insertion techniques (left atrial cannulation) and pt management. Since 1980, 12 pts have required LVA, nine have been weaned from the pump, and six pts have survived (50%). One pt has required RVA and has survived, and three pts requiring BVA did not survive. Seven pts have been alive and well 5, 9, 14, 19, 24, 30 and 36 months after surgery. Five are NYHA functional Class I status and two pts are NYHA Class II status. Current data indicates that single ventricular assistance in pts who cannot be weaned from CPB is "reasonable and therapeutic treatment to extend life."

Adult↗
PubMed1983

Clinical effectiveness of mechanical ventricular bypass in treating postoperative heart failure.

Our group has designed an air-powered, sac-type ventricular assist pump (VAP) that has a smooth polyurethane surface and Bjork-Shiley-type valves. This VAP has undergone extensive testing in calves and has been available for clinical use during the last 5 years. When properly employed, the circulatory support permitted immediate separation of the patient from bypass. Definite hemodynamic evidence of improved ventricular function has been observed during the period of unloading of the deranged ventricle by the VAP. However, during the first 3 years of our experience, the VAP was used in 11 patients with 1 survivor. During the last 2 years, specific attention has been directed to use of right, left, or biventricular assistance as indicated, to prompt application of the VAP when required, and to use of atrial rather than ventricular cannulation for VAP inflow. Accordingly, the survival rate over this 2-year period has increased to 50% (four of eight patients). The short-term assist pump is an important adjuvant for the surgeon who operates on seriously ill cardiac patients.

Aged↗
PubMed1983

Artificial hearts and blood pumps in the treatment of profound heart failure.

The recent clinical use of a pneumatic artificial heart at the University of Utah has focused attention on the role of blood pumps in the support of the circulation. Pneumatically powered assist pumps are now in clinical trials in patients with profound but reversible heart failure after open-heart surgery; survival rates as high as 50% in a heretofore lethal condition have been encouraging. The results of animal studies with the pneumatic artificial heart suggest that these devices are ready for clinical trials; the major application is likely to be as a bridge to cardiac transplantation. Implantable electric motor-driven assist pumps and artificial hearts are being evaluated in animals as permanent cardiac support or replacement devices; clinical use is projected to begin late in this decade. Initially, these devices will be employed in patients with end-stage cardiac disease who are not suitable candidates for cardiac transplantation or for whom donor hearts are not available. The availability of compact blood pumps will offer new forms of therapy to patients with certain types of profound heart failure.

Animals↗
PubMed1982

Vascular anastomoses in growing vessels: the use of absorbable sutures.

Primary end-to-end infrarenal aortic anastomoses were performed in 36 piglets using two synthetic absorbable suture materials: polydioxanone and coated polyglactin. Animals were killed at 1, 4, and 11 weeks and 6 months following operation. Each aorta was removed, burst-tested to 300 mm Hg, radiographed, and examined histologically. All anastomoses were patent, and no burst-test failures occurred. Stenosis occurred in 14 of 17 animals at 1 and 4 weeks, respectively. One of 5 animals exhibited stenosis at 11 weeks, and none of the 14 animals had stenosis 6 months postoperatively. Histological examination revealed fibrosis replacing areas of disrupted elastica at 6 months in both suture groups. This study suggests that absorbable suture material, in particular polydioxanone, because of its excellent handling characteristics and prolonged tensile strength retention, will be useful for the repair of vascular and cardiac anomalies where growth of the suture line is required.

Absorption↗
PubMed1981

Ventricular-assist pumping in patients with cardiogenic shock after cardiac operations.

A ventricular-assist pump was used to support the circulation in eight patients who could not be separated from cardiopulmonary bypass after open-heart operations. In five patients with left ventricular failure, the systemic circulation was maintained with pumping from the left atrium to the aorta for 7.0 +/- 1.8 days (mean +/- S.E.M.); three of these patients were well four to 17 months after surgery. In two patients with biventricular failure, right and left ventricular bypass supported the circulation, but neither patient survived. One other patient had isolated right ventricular failure; pumping from the right atrium to the pulmonary artery maintained the pulmonary circulation for 2.2 days. This patient lived for 18 months. Use of the ventricular-assist pump in our patients provided complete support of the systemic or pulmonary circulation or both. Profoundly depressed ventricular function is potentially reversible if technical problems in employing the pump can be avoided.

Adult↗
PubMed1981

Isolated partial anomalous venous connection: a congenital defect with late and serious complications.

The cases of 3 patients with partial anomalous pulmonary venous return with intact atrial septum are reported. The 2 adult patients had evidence of severe pulmonary artery hypertension with markedly increased pulmonary vascular resistance indicating advanced pulmonary vascular obstructive disease. This confirms earlier limited observations and emphasizes the potential for this congenital lesion to develop late, serious complications. In view of this potential, surgical repair of the anomaly should be considered whenever it is found. Descriptions of a successful operative approach are included.

Adult↗
PubMed1981

Electrochemical aging responses in pisum: cellular adaptations or recovery from injury?

Following excision, etiolated epicotyl segments of Pisum sativum L. cv. Alaska exhibit a marked hyperpolarization of membrane potential which is followed by a linear accumulation of K(+) when segments are incubated in Higinbotham nutrient solution. Segments aged for several hours and then reexcised display only a slight depolarization of membrane potential and no delay in ion accumulation; thus, recovery from injury appears an unlikely explanation for these responses. Substances originating in either the plumule or the cotyledons do not seem to be directly involved in these "aging" responses. However, locally produced substances, such as ethylene, or substances originating in the roots have not been eliminated as causative factors. Cold temperatures and cycloheximide prolong the lag in K(+) accumulation indicating a metabolic explanation for the induced K(+) accumulation. However, similar specific activities of plasma membrane-bound ATPase were found in isolates from fresh and aged epicotyl segments. Reactivation of an ion transport mechanism, perhaps responsible for the osmotic control of growth in immature cells, is suggested as a possible explanation for the pattern of ion accumulation characteristic of excised pea epicotyl tissue.

Journal Article↗
PubMed1981

Temporary left ventricular assistance in acute myocardial infarction and cardiogenic shock: rationale and criteria for utilization.

Left ventricular bypass may offer significantly better salvage of left ventricular myocardium in patients who remain hemodynamically unstable in spite of aggressive medical therapy and intra-aortic balloon support. Indeed, those 25 percent of patients refractory to intra-aortic balloon pumping may be salvageable with the prompt institution of left ventricular pumping assistance; however, just as early initiation of intra-aortic balloon pumping is critical, the early identification of balloon pumping failures and the institution of left ventricular bypass pumping may lead to a lower incidence of patients dependent on circulatory assistance and a higher rate of primary weaning. The results of left ventricular pumping assistance may indeed be totally different than those achieved with the intra-aortic balloon pump under these same conditions, because of the marked left ventricular unloading and hence the greater reduction in myocardial consumption of oxygen. The self-perpetuating cycle of progressive irreversible cardiac damage and shock may be broken, resulting in salvage of critical myocardial mass. Thus, cases of pumping dependence may be uncommon. There is also reason to believe that the heart without anatomically correctable lesions might function satisfactorily, but with a low cardiac reserve. Successful clinical application of left ventricular pumping assistance and subsequent analysis of therapeutic results demand a carefully devised protocol. This must be based on knowledge of the natural history of the disease and the results of previous sound clinical and experimental studies.

Acute Disease↗
PubMed1981

Primary vascular anastomosis in growing pigs: comparison of polypropylene and polyglycolic acid sutures.

Stenosis remains a significant problem in vascular anastomoses performed in the growing patient. This study compares the growth of vascular anastomoses performed with either polypropylene or polyglycolic acid sutures. End-to-end infrarenal aortic anastomoses were performed in 18 piglets. Twelve were performed with polypropylene; in six all sutures were placed in a continuous fashion (Group 1A), and in the other six the posterior sutures were continuous and the anterior were interrupted (Group B). Six anastomoses were performed with polyglycolic acid sutures placed in a continuous fashion (Group 2). The animals were killed 6 months following operation. The abdominal aorta was removed, measured, burst tested, and subjected to histologic studies. All anastomoses were patent. There were no burst failures at 300 mm Hg mean pressure. All polypropylene sutures in Group 1A and the continuous portion in Group 1B had straightened without breaking. Straightening without polypropylene suture breakage resulted in stricture in three Group 1A anastomoses and one Group 1B anastomosis; there was intraluminal polypropylene suture material in two Group 1A and five Group 1B anastomoses. Bowstring formation of the straightened, continuous portion of the polypropylene suture in two Group 1A anastomoses and one Group 1B anastomosis resulted in adherent thrombus. Group 2 anastomoses were without stricture and were grossly indistinguishable from adjacent normal vessel. Histologic examination showed varying degrees of chronic inflammation in the polypropylene anastomoses but negligible inflammation in the polyglycolic acid anastomoses. These results suggest that continuous suture techniques with polypropylene in growing vessels may result in stenosis and/or thrombosis. Moreover, synthetic absorbable polyglycolic acid sutures will be of use in vascular anastomoses in growing patients and in cases in which exacting technique with minimal postsurgical inflammation may be crucial to patency.

Animals↗