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Biomedical subjects

S Holme

Publications and source records attributed to S Holme.

86 records · Page 5Linked to original sources
PubMed1978

Evaluation of platelet tests for measurement of cell integrity.

Various tests were evaluated for their capacity to differentiate between platelet suspensions with different degrees of cell damage. Those suspensions were prepared by simultaneous isolation of platelets from the same platelet-rich plasma (PRP) using the following procedures: 1. centrifugation at 4 degrees C with EDTA 2. gel filtration in Tangen's buffer 3. gel filtration in Ca2+-free Tyrode's soltuion 4. gel filtration in Ca2+-free Tyrode followed by dehydration against polyethylene glycol 20,000 and 5. albumin density gradient centrifugation. In these suspensions and in the original PRP the following parameters were studied: 1. morphology; 2. aggregability upon ADP addition; 3. platelet factor 3 availability; 4. uptake of 14C-serotonin and 3H-adenine; 5. metabolism of 3H-adenine and adenylate energy charge; 6. endogenous total ATP, ADP and serotonin and 7. lactate dehydrogenase (LDH) activity. Quantitation of pseudopod formation in the light or electron microscope and log dose response studies for ADP-induced aggregation proved to be the most sensitive and reproducible of the tests studied. Additional information could be obtained from measurement of the 3H-label in the ATP and hypoxanthine-inosine fractions and calculation of the adenylate energy charge. Determination of platelet factor 3 availability or uptake studies of 14C-serotonin and 3H-adenine were less suitable for discriminating between cell suspensions. Data for total ATP and serotonin concentrations and LDH activity differed between the cell suspensions but instead of detecting various degrees of cell damage they reflected alterations in platelet population caused by the isolation procedures.

Adenine↗
PubMed1978

Platelet storage at 22 degrees C: effect of type of agitation on morphology, viability, and function in vitro.

Recovery in vivo after 51Cr labeling, platelet morphology, and platelet aggregation were studied with platelet concentrates (PC) stored for transfusion under carefully controlled conditions. PC were prepared to a final volume of 50 ml from whole blood anticoagulated with citrate-phosphate-dextrose (CPD). The platelet count was kept between 0.8 and 1.6 X 10(12) platelets/liter. The PC were stored in bags constructed of polyvinylchloride (PVC) or polyethylene (PE) at 22 degrees C for 72 hr. The bags were placed on a horizontal shaker or a ferris wheel for agitation during storage. No significant changes in pH or platelet count were observed during storage. PC stored on the wheel showed moderate loss of viability and a marked deterioration of platelet morphology and aggregation compared to the shaker. PC stored on the shaker in bags made of PE showed better aggregation with ADP and thrombin but had the same viability and morphology as PC in bags constructed of PVC. Maintenance of normal platelet morphology as determined by phase-contrast microscopy, extent of shape change response, and the size distribution according to the Coulter Counter correlated with recovery in vivo.

Blood Platelets↗
PubMed1977

ADP-induced refractory state of platelets in vitro. II. Functional and ultra studies on gel filtered platelets.

Gelfiltered platelets (GFP) in calcium free Tyrode solution containing albumin, glucose and adenosine deaminase were preincubated with 1 micronM 14C-ADP or 0.15 M NaCl (control) at 37 degrees C. The breakdown of extracellular 14C-ADP was markedly inhibited in this medium. No aggregation took place without fibrinogen, but the platelets underwent a disc to sphere transformation with development of refactoriness towards ADP. Presence of 2 mM CaCl2 in the incubation medium did not prevent refractoriness as reported earlier with washed rabbit platelets. When the ADP degrading enzyme, apyrase, was added at 30 min of incubation a partial recovery of the aggregability was observed. Electron microscopic studies showed that the partial restoration of the aggregation response, due to ADP degradation by apyrase, was accompanied by a return of discoidal morphology of the platelets. The ultrastructural studies showed further that spherical form with large number of pseudopods is not by itself a necessary or sufficient indication of platelets in a refractory state. However, the results indicated that spherical platelets are more vulnerable to external factors. It was concluded that refractoriness was mainly caused by a direct effect on the platelets by ADP itself, but the studies also suggested that deteriorating, irreversible, intracellular changes may take place when platelets are in spherical shape. An artificial medium, mechanical stress, incubation at 37 degrees C are factors that probably speed up these changes.

Adenine↗
PubMed1975

ADP-induced refractory state of platelets in vitro. I. Methodological studies on aggregation in platelet rich plasma.

ADP-induced aggregation was determined at various times of incubation with ADP in unstirred human platelet rich plasma (PRP) to which adenosine deaminase was added. In the early stages of incubation the shape change response was absent, the aggregation response was poor, and not reversible. These three parameters returned slowly towards normal as the incubation proceeded. Pronounced impairment of the aggregation response was present after all added ADP had been degraded in plasma. Log dose-response (rate of aggregation) curves for the platelets incubated with ADP had shifted to higher ADP concentrations and had also a small decrease in maximal height and in the slope compared to those obtained with control platelets. However, the shift in log dose response to higher ADP concentrations was far more striking, so the increase in log dose (R) necessary to obtain the same rate of aggregation as with control PRP was taken as a measure of refractoriness of aggregation towards ADP. R increased with the time of incubation to an optimal value and then decreased. The magnitude of the optimal value and the time at which optimum was reached increased with the concentration of the ADP incubated with the platelets. The variations in R during incubation did not correlate with the breakdown of added ADP. The platelets began to recover their ability to aggregate with ADP while there was still ADP in the system.

Adenosine Deaminase↗
PubMedDate not supplied

Paired comparison of the in vivo and in vitro results of storage of platelet concentrates in two containers.

Both in vitro and in vivo methods are used to test the validity of techniques for storing platelet concentrates for transfusion. In this study, the characteristics of platelet concentrates stored for 5 days at 22 degrees C in two different containers were evaluated by paired comparison using two in vitro measurements and two in vivo measurements. On two occasions, 10 normal subjects donated concentrates that were stored in containers of either the CLX system or the PL-146 system. The first plastic used was chosen at random. If necessary, a concentrate platelet count was reduced to 1,200,000 per microliters by addition of plasma to avoid pH fall. Mean recoveries were 48.2 +/- 10.6 percent (mean +/- 1 SD) and 42.4 +/- 7.8 percent for platelets stored in containers of the CLX and PL-146 systems, respectively. Similarly, survivals (T 1/2 in days) were 3.4 +/- 0.8 and 3.0 +/- 0.7, respectively. Since a paired design was used, the superiority of the CLX system was demonstrable with a one-tailed paired t test. If a paired design had not been used, a pooled t test would have been appropriate and the differences would not have been significant. This result emphasizes the value of the paired design. Furthermore, two in vitro measurements that reflect platelet morphology, dispersion of the size distribution and extent of shape change with adenosine diphosphate, were superior for platelets stored in CLX containers as well, suggesting a relationship between these measurements and in vivo viability.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMedDate not supplied

Evaluation of two instruments for noninvasive platelet concentrate quality assessment.

The Platelet Monitoring System (PMS) and the Non-invasive Assessment of Platelet Shape and Concentration (NAPSAC) instruments which relate light scattering characteristics of platelet concentrates (PC) to platelet concentration and shape, were evaluated to determine their accuracy in assessing platelet quality during storage from 1 to 7 days. The results were correlated with platelet concentration, % discs and pH on 121 PC stored in PL732 containers. NAPSAC output is in the form of platelet concentration and % discs. When NAPSAC and standard method values were compared, correlation coefficients (r) did not exceed 0.76 for counts and 0.62 for % discs. PMS output is in the form of lights with red indicating poor quality and green or amber indicating acceptable quality. Sensitivity of the PMS instrument did not exceed 83% and specificity did not exceed 63%. Mean platelet number, % discs and pH were comparable for units triggering red versus green or amber lights. In a separate study, 13 PL732 PC stored 5 days and transfused autologously were evaluated on the PMS. Three red light units exhibited recovery and survival times similar to those observed with PC triggering green/amber lights. These data indicate that neither instrument adequately assesses the quality of PL732 PC.

Blood Platelets↗
PubMedDate not supplied

Effect of an 8-hour holding period on in vivo and in vitro properties of red cells and factor VIII content of plasma after collection in a red cell additive system.

Extension of the holding time for whole blood units from 6 to 8 hours at ambient temperature should provide enhanced flexibility in the preparation of platelet concentrates (PCs). A paired study was conducted to evaluate the characteristics of stored red cells (RBCs) and plasma prepared from whole blood collected into a red cell additive system (CPD-ADSOL) after an extended holding time. An individual donated a unit of whole blood on two occasions; 1 unit was held for 6 hours before processing and the other for 8 hours. Autologous RBC 24-hour survival levels after 42 days of storage were comparable. Laboratory A, using a 99mTc-51Cr technique, found mean survival levels of 79 percent (6-hour hold) and 78 percent (8-hour hold) (n = 8). Analysis by the single-label procedure found the mean levels to be 82 and 81 percent. Laboratory B, using an albumin 125I-51Cr technique, found mean survival levels of 74 and 72 percent (n = 10). Mean hemolysis and ATP levels were found to be comparable after 42 days of storage following 6- and 8-hour holding periods. 2,3 DPG levels were reduced to a greater degree during the longer hold. The factor VIII levels in plasma frozen for at least a month after 6- and 8-hour holding periods were comparable; thawed plasma contained mean levels of 0.77 and 0.76 units per mL (n = 21). These studies indicate that components prepared by using a CPD-ADSOL system after holding periods of 6 and 8 hours have comparable properties.

Blood↗
PubMedDate not supplied

Quality of platelet concentrates.

Despite the current emphasis in transfusion medicine on regulatory compliance and cost containment, there is continuing activity in quality improvement of blood products. Quality can be assessed by measuring both benefit and risk. High quality products are those in which the benefit is maximized and the risk minimized. Risk, in the context of platelet transfusions, is minimized by reducing infectious agents, sources of allergic reactions, and other factors likely to cause adverse reactions in recipients. Benefit can be better described as potency. Potency is the ability to produce a desired effect. For platelet concentrates, potency has both quantitative [platelet yield] and qualitative [platelet viability, survival, and function] components. There are many activities which may influence the potency of the final transfused platelet product and these are summarized in Figure 1. It is helpful to review each step in order to assess the potential impact on the potency of the final transfused product.

Blood Platelets↗