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Biomedical subjects

G Rock

Publications and source records attributed to G Rock.

At least 127 records · Page 7Linked to original sources
PubMed1985

Comparative function of centrifugal apheresis devices.

The function of four apheresis devices has been evaluated to obtain comparative data on performance and safety. Granulocyte yields were highest with the CS-3000 with 1.7 X 10(10) cells, but this preparation also contained 4.5 X 10(11) platelets; plateletpheresis gave ranges of 3.4 X 10(11) to 4.5 X 10(11) cells. The amount of blood processed to obtain these yields varied greatly, ranging from 2.4 to 7 liters. Studies done on the donor return line showed no significant effects of the process. Comparative results on the efficacy of plasma exchange showed relatively little red cell contamination with any of these devices, but significant (6.9 X 10(10) platelet removal in the Fenwal bag.

Cell Separation↗
PubMed1985

Immune function in blood donors following short-term lymphocytapheresis.

Lymphocyte losses occur during repeat plateletpheresis and/or leukapheresis procedures and are potentially harmful to normal host immune function. This concern prompted us to study the effect of repeat lymphocytapheresis (lymphapheresis) on the immune system of healthy blood donors. Following a total of six lymphapheresis procedures over a 12-day period with removal of a mean of 41.6 X 10(9) lymphocytes, there were no significant changes in donor (n = 5) absolute lymphocyte counts, quantitative immunoglobulin levels or immune response capability as assessed by the following in vitro assays: percent of E, EA, and EAC rosette-forming cells, the percent of surface membrane immunoglobulin bearing cells, and the blastogenic responses to stimulation with phytohemagglutinin, pokeweed mitogen and concanavalin A. The procedures were well-tolerated without complications. During a follow-up period of 18 months, significant increases in total white cell counts (but not absolute lymphocyte counts), and in quantitative immunoglobulin levels (IgG, IgM, and IgA) were observed. The median increases in immunoglobulin levels ranged from 27.5% for IgG to 44% for IgA. We conclude that lymphapheresis as described is relatively safe and our results are reassuring in relation to lymphocyte losses that may occur during repeat cytapheresis procedures of normal blood donors.

Blood Donors↗
PubMed1985

Evaluation of a simple immunodiffusion technique for quantitation of platelet-associated immunoglobulin G in childhood immune thrombocytopenias.

Platelet-associated IgG (PAIgG) was quantitated in 33 children with immune thrombocytopenia and platelet counts less than 100 X 10(9)/liter using a simple radial immunodiffusion (RID) assay. Elevated PAIgG levels were found in 76% (16/21) of children with acute idiopathic thrombocytopenic purpura (ITP), 88% (7/8) of children with chronic ITP, and all four children studied with systemic lupus erythematosus and thrombocytopenia. Normal PAIgG values were found in children with the following disorders: malignancy and chemotherapy-related thrombocytopenia; ITP in remission (platelet counts greater than 150 X 10(9)/liter); various nonimmune hematologic disorders and juvenile rheumatoid arthritis, these children having normal platelet counts. In children with acute ITP, elevated PAIgG values at initial presentation fell to within the normal range when clinical remission occurred. The RID assay can be easily established in most hematology laboratories and has the advantage that solubilized "test" platelets used in the assay can be stored frozen prior to analysis. We conclude that this simple technique is of value in the evaluation of childhood thrombocytopenic states and yields results comparable to those reported using more complex antiplatelet antibody assays.

Adolescent↗
PubMed1984

Leukocyte-depleted blood: a comparison of available preparations.

Febrile nonhemolytic transfusion reactions due to leukoagglutinins are frequently seen in patients who have been given multiple blood transfusions. To prevent or reduce the severity of these reactions, leukocyte-poor blood (that containing fewer than 0.3 X 10(9) leukocytes per unit) is frequently requested by clinicians. Four methods commonly used in Canada to produce leukocyte-poor blood were examined for their relative effectiveness and appropriate use. The mean total leukocyte count per unit was reduced to 0.22 X 10(9) in buffy-coat-poor red blood cell preparations produced by centrifugation with the blood bag inverted, to 0.19 X 10(9) by perfusion through an Imugard filter, to 0.21 X 10(9) by the use of an IBM 2991 automated cell washer and to 0.13 X 10(9) with the use of frozen blood. The proportion of red cells recovered varied from 62% with the inverted-spin method to 85% with the use of frozen blood. Comparison of these data and the percentage of leukocytes removed, the shelf life of the product, the cost of supplies and the preparation time indicated that the use of sophisticated machinery, such as the IBM cell washer, or of glycerolization plus washing of frozen cells is not warranted for most patients. Instead, patients who have febrile nonhemolytic transfusion reactions should initially be treated with a leukocyte-poor red cell preparation produced by the inverted-spin method; only if such reactions recur should the blood bank be requested to provide filtered, washed or frozen red cells.

Blood Transfusion↗
PubMed1983

The relationship of biological and immunological activities of factor VIII.

Factor VIII is an essential blood clotting factor which consists of two protein moieties, each with distinct biological functions and antigenic determinants. The immunological markers were originally seen as indicators of the biological activities; however this view has been increasingly challenged. We have investigated the biological and immunological properties of Factor VIII to clarify these relationships. Plasma stored at room temperature for 21 days lost biological activity, but retained immunological activity: The procoagulant activity was reduced to 35% and the ristocetin cofactor activity to 75.4% of their original levels; but the reactivities of both procoagulant antigen and Factor VIII related antigen were maintained. A dissociation of activities was also demonstrated in serum, in which the procoagulant activity was 10% and the procoagulant antigen 72% of corresponding plasma values. These results indicate that the antigenic reactivities are not appropriate markers for Factor VIII biological activity.

Antigens↗
PubMed1981

Contamination of commercial blood products by di-2-ethylhexyl phthalate and mono-2-ethylhexyl phthalate.

Blood fractionation products obtained from three different manufacturers were analyzed to determine if either mono-2-ethylhexyl phthalate (MEHP) or di-2-ethylhexyl phthalate (DEHP) were contaminants of any of the fractionated proteins. The only protein fraction to contain DEHP was factor IX (23 micrograms/ml) from one company. However, MEHP was detected in low levels in several of the 5% normal serum albumin, 5% plasma protein fraction, factor VIII and factor IX samples. 25% normal serum albumin contained the highest level of MEHP with concentrations of up to 300 micrograms/ml (40% of the plasma level) depending on the sample. Attempts to remove MEHP using dialysis or ultrafiltration were unsuccessful and indicated a close association of the MEHP with albumin. There was a definite correlation between storage and transportation conditions and the level of MEHP in both plasma and 25% normal serum albumin. The highest levels of this phthalate acid ester were found in the products made from the plasma which had been shipped at ambient temperature. Contrary to published data, storage of plasma at -30 degrees C for up to 6 months prevented the accumulation of MEHP.

Blood Preservation↗
PubMed1981

Preparation of leukocyte-poor blood: a comparison of IBM 2991 washing and Huggins freeze-thawing.

Frequently, forzen blood is requested in order to provide a leukocyte-poor red cell transfusion and a reduced level of exposure to hepatitis virus rather than in an effort to find serological compatible red blood cells. However, this usage of frozen blood is expensive and, as recently reported, does not eliminate the risk of transmission of hepatitis. To assess the feasibility of substituting washed cell preparations, we have compared the Huggins frozen blood process with the IBM 2991 cell washing technique and have evaluated the efficiency of leukocyte removal and red cell recovery from homologous pools of fresh blood. The results of these experiments combined with the greatly decreased cost (approximately 1/3) and time required (approximately 1/6) indicate that many of the requests which blood banks receive for frozen blood could, in fact, be better met by using cells which have been washed in the IBM 2991.

Blood Preservation↗
PubMed1981

Accumulative effect of DDAVP and heparin in increasing plasma factor VIII levels.

DDAVP (l-desaminocysteine-(8-D-arginine)-vasopressin) produces a marked increase in plasma factor VIII procoagulant (F VIII:C) levels. Previously, we have reported that blood collected into heparin rather than into CPD anticoagulant results in higher starting levels of plasma F VIII:C activity. We therefore wished to determine whether the effects of these two agents were accumulative and whether they would result in any difference in the relative molecular distribution of F VIII:C. Blood was collected into CPD or heparin immediately before and 15 min after an intravenous dose of 0.2 micrograms/kg body weight of DDAVP. Pre-stimulation factor VIII levels were approximately 36% higher in heparinized plasma than in CPD plasma. Following DDAVP stimulation, the final factor VIII activity was increased 3.9-fold when either of the anticoagulants was used, with the heparin sample maintaining a 37% increase over the CPD sample. Column chromatography on Sepharose CL-6B of pre- and post-DDAVP plasma samples collected into either heparin or CPD indicated that there was no change in the relative distribution of the high and low molecular weight forms of F VIII:C. The heparinized sample showed the typical distribution of approximately 60% F VIII:C at void volume (Vo) and 40% at 2.3 Vo, suggesting that DDAVP-stimulated increases of plasma F VIII:C are equally distributed between the carrier and non-carrier associated F VIII:C activities.

Arginine Vasopressin↗
PubMed1977

Exogenous bacterial contamination of donor blood.

The Canadian Red Cross blood transfusion service has followed a set protocol for phlebotomy and collection of a unit of blood. Recent requirements for automated testing have necessitated that a second tube of blood be obtained from the blood line following collection of the unit. Evaluation of the techniques used, however, has indicated the possibility of bacterial contamination from the skin of donors, from insertion of the needle through an unsterile rubber stopper, and through backflow from a nonsterile vacuum tube. To test these possibilities swabs were taken from skin and stoppers of vacuum tubes. Further, vacuum tubes were deliberately contaminated with Escherichia coli. The normal sampling procedure, which involves stripping the donor line to refill and mix the blood, was then followed. This resulted in contamination of the segments and even the blood bag. These findings led to modification of the standard bleeding technique, whereby stripping was eliminated and sterile vacuum tubes were to be used at all times.

Antisepsis↗