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Biomedical subjects

G Rock

Publications and source records attributed to G Rock.

At least 91 records · Page 5Linked to original sources
PubMed1989

5-day storage of single-donor platelets obtained using a blood cell separator.

Platelets were collected from normal donors via a blood cell separator (Fenwal CS-3000). Platelets were stored initially in two separate 1000-ml bags (average count per bag, 2.3 +/- 0.5 x 10(11)) in 100 ml of autologous plasma for 5 days. Little change in platelet count was noted after 5 days of storage; however, the white cell count fell from 5.1 +/- 1.7 x 10(9) at Time 0 to 3.4 +/- 2.3 x 10(9) per l at Day five. The initial lactate values were 32 +/- 11 mg per dl and rose to 165 +/- 28 mg per/dl by 5 days. Platelet aggregation was impaired both by the collection procedure and during storage: whereas the response to ADP of the donors' platelets before the procedure was 100 percent, samples taken from the product immediately after collection had only a 45 percent response, which fell to 12 percent by Day 5. Aggregation using epinephrine was similarly affected, with a 75 percent response after collection and 0 percent response by Day 5. The plasma beta-thromboglobulin (beta-TG) level was high, both after collection (5.0 micrograms/ml at Time 0) and after storage (11.0 micrograms/ml), indicating a considerable effect of collection on platelet alpha granule release. In vivo recovery of these platelets was very good at 67 +/- 6 percent, with an average survival of 7.3 +/- 1.4 days (multiple hit; n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Component Removal↗
PubMed1989

5-day storage of platelets collected on a blood cell separator.

One of the earliest devices available for plateletpheresis is the Haemonetics system; this machine has been updated recently to permit the use of software in a closed system and thus storage of the collected platelets beyond 24 hours. The authors examined the in vitro and in vivo function of platelets collected on the Haemonetics AutoSurge machine and stored for 5 days in two separate 1000-mL CLX bags. The average count per bag was 1.8 +/- 0.4 x 10(11) in approximately 200 mL of plasma. Immediately following collection, the platelet response to ADP and epinephrine represented 78 and 35 percent, respectively, of the preapheresis values. Aggregation to single stimuli subsequently decreased to 29 and 0 percent, respectively by Day 5. This response is equal to or better than the response reported with the Fenwal CS-3000, the only other plateletpheresis device routinely used for long-term storage. The pH of the preparations was well maintained throughout storage, and there was little alteration in hypotonic shock response or serotonin uptake. Serotonin release decreased consistently. The morphology scores indicated good maintenance of shape immediately following collection; this subsequently decreased after 5 days of storage. Bacterial cultures were negative in all instances. The 51Cr in vivo survival and recovery was good with 65.5 +/- 7.1 percent recovery and an average survival of 7.3 +/- 1.3 days (multiple hit; n = 5). The data indicate that storage of the Haemonetics plateletpheresis product is feasible and that the product is as good as others currently available.

Blood Component Removal↗
PubMed1989

Perioperative exposure to plasticizers in patients undergoing cardiopulmonary bypass.

Di(2-ethylhexyl)phthalate and its principal metabolite, mono(2-ethylhexyl)phthalate, are contaminants of blood that are extracted on contact with polyvinylchloride surfaces, such as blood collection bags and tubing used in cardiopulmonary bypass. In this study, levels of the two plasticizers were measured in patients who underwent coronary artery bypass grafting, orthotopic transplantation, implantation of the Jarvik 7-70 total artificial heart during bridge-to-transplant procedures, and in infants who underwent corrective operations for congenital defects. In all adult patients the levels of di(2-ethylhexyl)phthalate increased tenfold by the end of cardiopulmonary bypass, whereas the levels of mono(2-ethylhexyl)phthalate increased ninefold. In infants, levels of di(2-ethylhexyl)phthalate rose seven times by the end of bypass and mono(2-ethylhexyl)phthalate rose significantly as well. In most of the patients having coronary bypass, the two plasticizers declined to preoperative levels within 24 hours. However, in some of the patients having orthotopic transplantation and in those in whom the Jarvik 7-70 total artificial heart was used as a bridge to transplant, the levels were still detectable 120 hours postoperatively. Circulating levels of mono(2-ethylhexyl)phthalate are only 20- to 35-fold lower in patients undergoing cardiac operations than the level of mono(2-ethylhexyl)phthalate causing a 50% reduction in developed contractile force and arrhythmias in an in vitro human atrial trabecular preparation. This study shows that patients with multisystem failure and infants may be at risk for this acute exposure to mono(2-ethylhexyl)phthalate.

Cardiac Surgical Procedures↗
PubMed1988

Human factor VIII from heparinized plasma. Purification and characterization of a single-chain form.

Human factor VIII was purified from heparinized blood by cryoprecipitation, poly(ethyleneglycol) precipitation, Affi-Gel blue, aminohexyl, polyelectrolyte E5 and immunoaffinity chromatography. A purification of 280,000-fold over plasma with a specific activity over 5300 units/mg was achieved. Analyses of factor VIII using HPLC indicated a molecular mass of 280-340 kDa. Variation in the native mass may reflect heterogeneity of the protein due to associated lipid since structural analysis confirmed that factor VIII contained variable amounts of free fatty acids and diglycerides and triglycerides, but no phospholipids. Additional characterization by denaturing polyacrylamide gel electrophoresis under reducing conditions, followed by silver staining, showed a major single-chain polypeptide of factor VIII with a mass of approximately 260 kDa. To determine whether proteolyzed forms of factor VIII were present during fractionation, we analysed earlier steps in purification. This revealed additional species of factor VIII eluting faster than the single-chain form during chromatography on polyelectrolyte E5. Gel electrophoresis showed that these species of factor VIII consisted of multiple polypeptide chains, and partial peptide mapping using Staphylococcus aureus V8 protease indicated that they were structurally related. Monoclonal and hemophilic antibodies were used in immunoadsorption experiments to demonstrate that the purified factor VIII was composed predominantly of the 260-kDa factor VIII chain.

Chromatography, Affinity↗
PubMed1988

Abnormal platelet von Willebrand factor interaction in patients with TTP.

Thrombotic thrombocytopenic purpura (TTP) is associated with abnormal platelet function and disturbances in coagulation; however, a specific causative factor is not defined. Plasma infusion or plasma exchange (PE) are thought to be of benefit in replacing a deficient plasma component or removing some toxic compound. In three patients with TTP, samples taken prior to initiation of PE showed high levels of vWF:Ag in the plasma (208, 264, and 321 U/dl), whereas the VIII:C levels were normal. The vWF:Ag multimer patterns of the plasma demonstrated a decrease in the amount of high molecular weight (HMW) forms. Analysis of the platelets from one patient also showed an increase in the HMW multimers. Platelets from all three patients showed a decreased ability to absorb vWF:Ag, with little or no absorption of the HMW forms. Following extensive PE and resolution of disease, the platelets regained their ability to absorb vWF:Ag in the one patient examined.

Adult↗
PubMed1988

An antibody to platelet membrane antigen associated with thrombotic events in essential thrombocythemia.

A 71-year-old man with essential thrombocythemia presented with acute onset of thrombosis in his fingers. The platelet count at presentation was 752 x 10(9)/liter, and his PTT was within the normal range. Platelet aggregation was normal in response to ADP, decreased to epinephrine, and absent to collagen, with the patient receiving 1.2 g aspirin/day. Plasma vWF:Ag was 158 U/dl, VIII:C was 150 U/dl, and the vWF:Ag multimer pattern was normal. HLA antibodies were not detected in his serum, and the platelet-associated IgG was normal at 3.9 fg/platelet. Incubation of normal, unactivated platelets with the patient's plasma did not result in agglutination of the platelets. However, a serum antibody reacting against a platelet antigen with an apparent molecular weight of 45,000 could be demonstrated by Western blotting. This antibody also reacted with endothelial cells. The reactive pattern was similar to that of commercially obtained actin; the serum antibody could be removed by preincubation with actin. Platelet-plasmapheresis was carried out daily for 10 days, after which the serum still reacted weakly with the platelet antigen. By day 20, the band could still be identified on the electroblot, but 2 weeks later no band could be seen. Similar assay of sera from six other patients with myeloproliferative disorders and comparable thrombocytosis but without thrombotic manifestations did not show any such reactions. The data suggest a correlation between the presence of an antibody possibly directed against platelet and/or endothelial cell actin and the vascular events in this patient with essential thrombocythemia.

Aged↗
PubMed1988

Logistics of automated plasma collection.

Plasmapheresis is widely carried out to produce plasma for fractionation. Production of Factor VIII and albumin, two proteins in plasma, drives the plasma industry. The Canadian Red Cross would like to achieve national self-sufficiency in plasma production to meet the rising demands for these proteins in the next 4 years. In order to achieve this goal we must make efficient use of our automated plasmapheresis machines and available human resources to produce a cost-effective plasma product. An assessment was undertaken at the Ottawa Centre to evaluate the number of procedures which could be performed on each machine per day and the staff required to operate these machines safely and efficiently. Donor availability, reliability and reasons for donating plasma were recorded to determine if our population could support such an escalated programme. Donor/staff interest and acceptance of automated equipment was determined. The results showed that four automated plasmapheresis devices could be operated by one nurse and one clinic assistant processing 32 donors a day with an average time of 27 min required for a 500-ml donation of plasma. The donor population was available and extremely interested; however, the logistics of scheduling proved to be an area for concern requiring special attention.

Autoanalysis↗
PubMed1988

Effectiveness, specificity and safety of intranasal 1-deamino-8-D-arginine vasopressin treatment of normal blood donors.

A study of the absorption of 300 micrograms of 1-deamino-8-D-arginine vasopressin (DDAVP) given intranasally to normal blood donors was carried out to determine (a) the correlation between plasma levels of DDAVP and the percent rise of factor VIII procoagulant activity (VIII:C) and (b) the efficacy, specificity and safety of this treatment in increasing the recovery of factor VIII:C in donated blood. The maximum drug concentration was highly correlated to the maximum percent rise of VIII:C (r = 0.858, p less than 0.01). A differentiated effect of DDAVP on increases of VIII:C, VIII:Ag, vWF:Ag and vWF multimers was observed. A transient rise of fibrinopeptide A from 5 to 16 ng/ml, 30 min post-DDAVP, was not accompanied by changes in fibrinogen levels or generation of detectable factor Xa or thrombin. DDAVP had no effect on the factor XII-dependent pathway of plasminogen activation, or on the donor's vital signs and hematological parameters. Side effects were minor and of short duration. Intranasal DDAVP treatment of blood donors is considered to be a practical means of improving the recovery of VIII:C from normal donors.

Administration, Intranasal↗
PubMed1988

A linkage study of primary affective disorder.

Marker loci in 113 members of nine unrelated multiplex families identified by a bipolar proband were tested for linkages with primary affective disorder. Linkage was excluded between the disease locus (assuming that it was a single autosomal dominant gene) and the HLA loci at a recombination fraction of 0.2, the ABO, Rh, and Lu loci at almost 0.05 and the Fy and P loci at 0.001.

Adult↗
PubMed1988

Inhibition of human platelet phospholipase A2 by mono(2-ethylhexyl)phthalate.

There is evidence that the carcinogenic and teratogenic effects attributed to the plasticizer di(2-ethylhexyl)phthalate (DEHP) are due to its major metabolite mono(2-ethylhexyl)phthalate (MEHP). MEHP is also formed ex vivo by a plasma enzyme in blood products stored in polyvinyl chloride (PVC) DEHP plastic containers. People who receive large amounts of blood products, such as hemophiliacs or patients undergoing hemodialysis, cardiopulmonary bypass, or massive transfusion, are exposed to significant levels of plasticizer. In this study, the platelet was used to show that MEHP inhibits phospholipase A2 (PLA2), one of enzymes important in the release of arachidonic acid from membrane phospholipids. Arachidonate is the parent molecule for the synthesis of prostaglandins, thromboxanes, leukotrienes, and lipoxins that are made by a wide variety of cells. PLA2 was measured by the liberation of 14C-arachidonic acid from 1-stearoyl-2-[1-14C]arachidonyl-L-3-phosphatidylcholine. MEHP inhibits PLA2 activity noncompetitively in intact human platelets and lysates with a Ki of 3.7 x 10(-4) M. DEHP does not inhibit PLA2 in whole platelets. Inhibition of PLA2 by MEHP occurs at only three times the circulating level of MEHP measured in neonates undergoing exchange transfusion and 20-fold the levels experienced by patients during cardiopulmonary bypass. Therefore, infants and adult patients with multisystem failure who accumulate MEHP in their blood may be at risk for decreased platelet function.

Blood Platelets↗
PubMed1988

Automated contrast fluorometry. I. Lymphocytotoxicity testing.

Automated contrast fluorometry has been carried out in lymphocytotoxicity testing using a computer-controlled microscope and direct comparison of the data with controls. The method uses heparinized lymphocytes and permits simultaneous evaluation of both fluorescein and ethidium bromide fluorescence by calculating the quotient between the green/red measurements. After comparison of the quotient with that of control samples, the raw data are automatically transformed into cytotoxicity scores. Fast and reliable measurements with minimum background fluorescence can be obtained for up to 24 hours after performance of the assay by controlling complement reactivity and the exposure time of the cells to the fluorescein. The evaluation of 15,204 cytotoxic reactions showed excellent correlation between the automated and visual results of 125 tissue typings using 120 different antibodies and of 17 HLA antibody titers using case-by-case analysis of variance. The values for the automated cytotoxicity readings were slightly higher and showed more intermediate scores than those of the visual readings suggesting a high sensitivity and objectivity of the automated system. In conclusion, this is a methods paper comparing parallel lymphocytotoxicity testing using automated and manual methods. The automated method was found to be more sensitive and faster than the manual method.

Automation↗
PubMed1987

Registry of unrelated bone marrow donors.

Reports of successful transplantation of bone marrow obtained from unrelated donors who were histocompatibility leukocyte antigen (HLA) identical prompted the Canadian Red Cross Blood Transfusion Service in Ottawa to assess the possibility of developing a bone marrow donor registry in Canada. We sent a pamphlet that explained the program to 1568 people who had undergone apheresis and asked them to reply, stating their interest. At the same time the pamphlets and a poster were placed in the blood donor clinic. We received 1232 replies (78.6%) from the apheresis donors, 838 (68.0%) of which indicated a willingness to attend information sessions. Of the 7158 people who gave blood during the 3-month study period, 225 (3.1%) were interested. At the time this paper was written 47 information sessions had been held, and 721 people had attended, 624 (86.5%) of whom had signed a consent form. This indicates a clear interest in a bone marrow donation program. We believe that the ethical issues are overcome by requesting the donation before identification of any patient. From our experience a national registry of unrelated donors seems feasible, and steps are being taken to implement such a program.

Blood Component Removal↗