Search PubMed⌕ Search

Biomedical subjects

G Rock

Publications and source records attributed to G Rock.

At least 109 records · Page 6Linked to original sources
PubMed1987

Use of platelet concentrate in eastern Ontario.

To better understand the reasons for the increasing use of platelet concentrate in Canada, we undertook a 4-month study of platelet concentrate transfusion in six eastern Ontario hospitals in 1985. A total of 4801 units of platelet concentrate were transfused on 687 occasions to 303 patients; the average number of transfusions per patient was 2.3, the average number of units per transfusion 7.0 and the average number of units per patient 15.8. The cardiovascular service used the largest proportion of units (28%), aortocoronary bypass grafting being the most common procedure. The mean pretransfusion platelet count for the medical and oncology services was about 30.0 X 10(9)/L, compared with 155.5 X 10(9)/L for the cardiovascular service. An increment in platelet count 1 hour after transfusion was noted with 238 (75%) of the transfusions for which the data were available; the average increment was 3.4 X 10(9)/L per unit of platelet concentrate transfused. When the data for patients who did not respond were excluded, the average increment was 6.9 X 10(9)/L. Single-donor platelet concentrate was requested for only half of the transfusions to which no response was detected. The current medical literature supports the appropriate use of platelet concentrate in patients with thrombocytopenia due to chemotherapy, but prophylactic platelet transfusion for patients undergoing cardiovascular bypass procedures is being questioned. We advise continued surveillance of the use of these products and re-evaluation of the aims of platelet transfusion therapy.

Blood Transfusion↗
PubMed1987

Measurement of human factor VIII by avidin-biotin dot immunobinding ELISAs.

Hemophilia A is a congenital bleeding disorder which is characterized by a functional deficiency of the coagulation protein factor VIII. We have developed sensitive enzyme-linked immunosorbent assays (ELISAs) for measuring the antigenic reactivity of factor VIII. The assays utilize dot immunobinding techniques, commercial monoclonal antibodies, and a detection system enhanced by the interaction of avidin and biotin. The dot immunobinding ELISAs were optimized for measuring factor VIII in normal and hemophilic plasma, and in partially and highly purified preparations of factor VIII. Linear standard curves were established for all samples, defining the range for accurate measurement. Factor VIII was detected at concentrations as low as 0.0005 U/ml, which represents 0.1 pg of protein.

Antibodies, Monoclonal↗
PubMed1987

Electroblotting and immunohistochemical staining for identification of platelet antibodies.

The Western blot procedure has been adapted for use with a biotinylated antiglobulin reagent and a horseradish peroxidase complex (Vectastain ABC) to determine specific sites of antigen binding and permit discrimination between various types of platelet antibodies. Monospecific anti-PlA1 antisera or sera containing mixtures of multispecific HLA and unidentified platelet specific antibodies were tested with PlA1 phenotyped platelets. Using monospecific anti-PlA1, one intense band with relative molecular weight (Mr) of 88,000 and corresponding to glycoprotein IIIa was seen with the PlA1+ platelets. With mixtures of antibodies, reactions were seen with platelet specific antibodies without interference from the HLA antibodies; with one serum a band of Mr approximately 135,000 was identified with Baka+, but not Baka- platelets, indicating the presence of an anti-Baka in the serum. The location of the Baka antigen corresponded to the area for GP IIb. With another serum, a band of Mr 88,000 was revealed with PlA1- and some PlA1+ platelets suggesting the presence of an anti-PlA2. Two additional bands of Mr 160,000 and 200,000 were present on all preparations including autologous controls, probably due to the presence of non-specific IgG. Thus, immunohistochemical staining is readily adaptable to the Western blot technique, and antibodies to platelet-specific antigens can be easily differentiated from HLA antibodies.

Antibodies↗
PubMed1987

Is serum the optimal source for HLA antibodies?

The cytotoxic reactivity of 18 predefined class I HLA serum antibodies was compared with that of antibody preparations containing anticoagulants. ACD-A, EDTA, 4% citrate and heparin plasmas all showed lower cytotoxicity than serum antibodies. Recalcification of both platelet-rich and platelet-poor ACD-A plasma did not fully restore the antibody reactivity, suggesting a detrimental effect of calcium chelation. This effect was exclusive of volume or of any platelet or plasma protein involvement. The changes in pH contributed to the lower reactivity and to the increased lympholytic effect, whereas adjusting the pH toward the serum value improved the reactivity. Heat-inactivated antibodies showed only a slightly reduced cytotoxicity. Heparin had the least effect of all anticoagulants on the reactivity, although in heparin there was a definite dose-dependent decline in cytotoxic titer which was probably related to anticomplementary activity. Calcium chelators, such as EDTA and citrate, showed marked cytotoxic inhibition at half the usual complement concentration. This effect was more pronounced when the anticoagulant and lymphocytes were incubated prior to cytotoxicity testing. At the complement concentrations used, the inhibitory effects of the citrate anticoagulants appeared to be primarily calcium-related. Inhibition tests, serial titrations and testing of varying calcium concentrations confirmed the superiority of serum as antibody source.

Anticoagulants↗
PubMed1987

5-day storage of human platelet concentrates in 30 ml of plasma or artificial medium.

Optimal conditions for the storage of platelet concentrates were studied by changing 5 environmental parameters: bag composition (PL146 vs. PL732), volume of plasma (60 vs. 30 ml), anticoagulant (CPDA-1 vs. heparin), nutrient (glucose vs. fructose) and medium (plasma vs. artificial medium). A full bilevel factorial study was conducted to evaluate each variable alone and in combination with the other variables for their effects on platelet aggregation and release in response to single and pairs of stimuli. Serotonin uptake, pCO2, platelet count, lactate, glucose, pO2, pH and white blood cell concentration were also measured after 3 and 5 days of storage. Platelets that were stored in PL146 bags had reduced responses to stimulation by 3 days and markedly impaired responses after 5 days relative to platelets that were stored in PL732 bags. There was a large drop in pH and platelet responsiveness when platelets were stored in a volume of 30 ml in PL146 bags; these were not found when platelets were stored in 30 ml in PL732 bags. Replacing plasma with an artificial medium or adding fructose or heparin and calcium to plasma yielded platelets that were equally functional as routine controls in CPD-A1 plasma. It was concluded that replacement of plasma with 60 ml of artificial medium or a reduction of plasma volume with storage in PL732 bags are two possible mechanisms of obtaining more plasma from blood donations without compromising maximum platelet storage life.

Anticoagulants↗
PubMed1987

The effect of the plasticizer di(2-ethylhexyl)phthalate on red cell deformability.

Red cell concentrates (RCC) are stored for 35 to 42 days in plastic containers manufactured with the liquid plasticizer di(2-ethylhexyl)phthalate (DEHP). DEHP leaches from the polyvinylchloride (PVC) plastic bag, then binds to and stabilizes the RC membrane. This study was undertaken to determine the deformability of the RC membrane using an osmotic gradient ektacytometer and to relate these measurements to the concentration of DEHP in the stored RCC. Pooled RCC was aliquoted into PL146 (PVC), PL732 (polyolefin), and PL732 (with added DEHP) bags with samples removed weekly for analysis of osmotic fragility, deformability, and DEHP concentration. The adenosine triphosphate (ATP) content was also measured. The increase in osmotic fragility during storage was greater when RCC was stored without DEHP. In addition, there was a decrease in the maximum elongation index (El max) when there was decreased DEHP in the storage bag. The osmolarity (Omax) at which El max occurred, as well as the Omin, the osmolarity at which minimum elongation (El min) occurred was higher in the PL732 container than in the PL146 or in the PL732 to which DEHP had been added. These changes could be reversed by addition of DEHP at the beginning of the storage period, showing a direct correlation between DEHP concentration during storage and RC membrane flexibility. By a better understanding of the mechanism of DEHP protection, it might be possible to substitute a less toxic stabilizing compound.

Adenosine Triphosphate↗
PubMed1986

Contamination of platelet storage bags by phthalate esters.

Phthalate esters are the most extensively used plasticizers in the manufacture of polyvinylchloride (PVC) plastic. Many medical devices used in the collection and storage of blood components are made of PVC plastic containing di(2-ethylhexyl) phthalate (DEHP). DEHP leaches at a rate of 100 micrograms/ml X d into platelet concentrate (PC) supernatant when PCs are stored in PVC containers. It is only possible to store PCs for 72 h in this DEHP plastic, after which time the platelet function has deteriorated and they cannot be used for transfusion therapy. Since it was desirable to find a container that permitted longer storage times and because of the concern for the toxicity of DEHP, new bags, manufactured with different plastic formulations without this plasticizer, were tested for PC storage. Using these new containers, such as the PL732 [polyolefin (PO) plastic], and the CLX300 and PL1240 [tri(2-ethylhexyl) trimellitate (TEHTM) PVC plastic], it was possible to store PCs for 5 d while preserving platelet function. In spite of these new plastic bags being manufactured without DEHP, we found DEHP and its metabolite mono(2-ethylhexyl) phthalate (MEHP) as contaminants of the supernatant of the PCs stored in these containers. After analyzing the plastic material of each of these containers, we were able to identify the source of the contamination as coming from the plastic materials that were used in the manufacture of the bags. The sterilization process of the PL732 bag was investigated, since it was found that when the plastic of the PL732 bag was analyzed prior to sterilization, no contamination by DEHP was detected; however, whether the PL732 bag was sterilized together with the primary PVC bag or separately, using ethylene oxide, contamination by DEHP was found, suggesting contamination of the sterilization unit by DEHP.

Blood Platelets↗
PubMed1986

Distribution of di(2-ethylhexyl) phthalate and products in blood and blood components.

In order to impart flexibility, plastic medical devices incorporate liquid plasticizers into their structure. Data from several laboratories, including ours, have shown that these compounds leach from blood bags and tubing during collection of blood, storage of various blood components and during kidney dialysis and cell and plasma apheresis procedures. After the plasticizer di(2-ethylhexyl) phthalate leaches from poly(vinyl chloride) blood packs, it is converted by a plasma enzyme to a more toxic metabolite, mono(2-ethylhexyl) phthalate. Blood fractionation products from outdated plasma contain mono(2-ethylhexyl) phthalate, the highest level being found in normal serum albumin. Recently, we have reported that di(2-ethylhexyl) phthalate actually binds to the red blood cell membrane and reduces its osmotic fragility. Current methods of red cells storage, which permit utilization up to 35 days after collection, are not possible without this membrane stabilization. Platelets are now stored for 5 days in the Fenwal PL 732 polyolefin bag. Although stated to be essentially free of liquid plasticizers, a significant level of leaching from this bag into the extracts of stored platelet concentrates was observed.

Blood Platelets↗
PubMed1986

Survival and recovery of human platelets stored for five days in a non-plasma medium.

Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

Blood Platelets↗
PubMed1985

Disparity between one- and two-stage factor VIII assays in measuring VIIIC in heparinized plasma.

The level of Factor VIII procoagulant activity (VIIIC) was found to be more than 30% higher in heparinized plasma than in citrated plasma from the same donor when determined by a one-stage assay (1.34 U/ml versus 1.0 U/ml). However, after Al(OH)3 adsorption and two-stage assay, the VIIIC levels were not significantly different for the two types of plasma (0.90 +/- 0.25 U/ml versus 0.82 +/- 0.23 U/ml). If a one-stage assay was employed after adsorption, a similar low result was obtained (0.92 +/- 0.21 U/ml versus 0.91 +/- 0.12 U/ml). This indicated that the adsorption step itself was responsible for the difference in results. Parallel analyses of other VIII markers demonstrated that more VIIIC antigen (VIIICAg) was removed by adsorption of heparinized rather than citrated plasma (0.33 U/ml versus 0.12 U/ml) although there was no difference in the level of VIII-related antigen (VIIIRAg). The results show that adsorption of heparinized plasma prior to either one- or two-stage assay leads to a greater loss of both VIIIC and VIIICAg activity than observed with citrated plasma and indicate that, when applied to heparin plasma the two-stage assay for VIIIC underestimates the actual VIIIC content.

Adsorption↗
PubMed1985

An in vivo assessment of factor VIII concentrates.

Replacement therapy for patients with hemophilia A requires that a specific dose of factor VIII be administered. Generally, these calculations involve the use of the manufacturer's stated dose in an equation. We have assessed factor VIII concentrates by in vitro techniques and found a considerable discrepancy (35%) between the stated and the measured contents. Confirmation of this discrepancy was obtained by in vivo assessment where posttransfusion recoveries corresponded to the measured rather than the stated contents of the vial. The half-disappearance time ranged from five to eight hours. The data suggest that constant monitoring of factor VIII preparations is necessary to ensure optimal treatment of patients with hemophilia A and help to explain the recent efforts by the Office of Biologics to achieve standardization.

Adult↗
PubMed1985

Plasmodium falciparum malaria mimicking autoimmune hemolytic anemia during pregnancy.

A 30-year-old woman contracted Plasmodium falciparum malaria in the first trimester of her pregnancy while taking chloroquine for malaria prophylaxis. Her illness was characterized by hemolytic anemia with IgG1 coating of the surface of the erythrocytes and IgG3 in her serum. The hemolysis subsided following treatment of the malaria infection early in the third trimester. She delivered at term an infant who had hypoplasia of the right tibia and fibula and absence of the fifth ray of the right foot. The hemolytic process was attributed to the malaria infection, and the birth defect may have been related to the antimalarial therapy in the first trimester of pregnancy.

Abnormalities, Drug-Induced↗
PubMed1985

Alternate dosage regimens for high molecular weight hydroxyethyl starch.

Six percent high molecular weight hydroxyethyl starch (HES) was used in the standard 500 ml dose and in various decreased doses to assess the efficacy of alternate dosage regimens for granulocyte procurement. When used in full strength, yields of 0.57 +/- .15 X 10(10) per liter of blood processed (LBP) were obtained. When HES was used on only the first three passes, the subsequent three passes, done with Anticoagulant Citrate Dextrose Solution USP Formula A (ACD-A); Fenwal Laboratories, Deerfield, IL), reduced the yield to 0.14 +/- .06 X 10(10)/LBP. Reversing this procedure gave yields of 0.06 +/- .05 X 10(10)/LBP (without HES) and 0.49 +/- 0.36 X 10(10)/LBP when HES was added during the next three passes. When the HES dose was reduced to half-strength on the second consecutive day of leukapheresis, the granulocyte yields were reduced from 0.57 +/- .15 X 10(10)/LBP to 0.42 +/- .07 X 10(10)/LBP. Use of half-strength HES on virgin donors gave yields of only 0.35 +/- .39 X 10(10)/LBP. Infusion of the entire 500 ml dose of HES 1/2 hour prior to the procedure produced low yields of 0.20 +/- .12 X 10(10)/LBP, indicating that HES must be present during the centrifugation and separation procedure in order to enhance yields. The data suggest that alternate dosage regimens of this form of HES are not advisable and that optimal yields are produced when 500 ml of the six percent solution is used during the collection procedure.

Granulocytes↗