Search PubMed⌕ Search

Biomedical subjects

G Rock

Publications and source records attributed to G Rock.

157 records · Page 9Linked to original sources
PubMedDate not supplied

Modified fluid gelatin. An alternative macromolecular agent for centrifugal leukapheresis.

We studied a French modified fluid gelatin (MFG), substituting it for hydroxyethyl starch (HES) in leukapheresis procedures using three currently available blood cell separators, and observing its effects on the function of platelets and granulocytes. As a cell-collecting agent, we found MFG to be as effective as HES with intermittent flow centrifugation (Haemonetics), and slightly less so with one continuous flow device (IBM 2997). MFG was clearly less effective than HES with the Fenwal CS-3000 continuous flow separator, although we have reason to believe it would be possible to improve efficiency with this machine by changing the operating variables. Tests of platelet and granulocyte function showed negligible alteration with either agent and no difference between them. MFG disappears much more rapidly from the circulation than HES (after a single injection, it is undetectable by the third day). Reaction frequency with MFG was about the same as that of HES, with perhaps somewhat more frequent allergic manifestations.

Blood Platelets↗
PubMedDate not supplied

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 +/- 0.15 X 10(10) per 1 of blood processed (LBP) were obtained. When HES was used in only the first three passes, the subsequent three passes, done with acid-citrate-dextrose, Formula-A (ACD-A, Fenwal Laboratories, Deerfield, IL), reduced the yield to 0.14 +/- 0.06 (mean +/- SD) X 10(10) per LBP. Reversing this procedure gave yields of 0.06 +/- 0.05 X 10(10) per LBP (without HES) and 0.49 +/- 0.36 X 10(10) per LBP when HES was added during the next three passes. When the HES dose was reduced to one-half strength on the second consecutive day of leukacytapheresis, the granulocyte yields were reduced from 0.57 +/- 0.15 X 10(10) per LBP to 0.42 +/- 0.07 X 10(10) per LBP. Use of one-half strength HES on first-time donors gave yields of only 0.35 +/- 0.39 X 10(10) per LBP. Infusion of the entire 500-ml dose of HES one-half hour prior to the procedure produced low yields of 0.20 +/- 0.12 X 10(10) per LBP, indicating that HES must be present during the centrifugation and separation procedure in order to enhance yields. These 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 6 percent solution is used during the collection procedure.

Blood Specimen Collection↗
PubMedDate not supplied

Platelet storage in a plasma-free medium.

Currently, platelet concentrates are stored in 50 to 60 ml of plasma. A major drawback to storage in plasma is the considerable loss of platelet function which occurs during storage. A modified Tyrodes medium has been developed for storage of platelets. A comparison between platelet concentrates stored in this medium and in plasma showed that platelet aggregation and release responses to synergistic pairs of stimuli were equivalent for both types of concentrates on the day of preparation and after 72 hours. Platelet aggregation and release responses to single stimuli, the content of membrane glycoproteins, and the pH declined during storage but were similar for both preparations. The data show that plasma is not required to maintain in vitro platelet function during storage of platelet concentrates, but in vivo functions remain to be determined. The use of an artificial medium has the advantages of decreasing patient exposure to plasma contaminants, generating additional plasma for fractionation, and controlling more exactly the storage environment.

Blood Platelets↗
PubMedDate not supplied

Donor variables affecting survival of autologous platelets.

While platelet survival studies have been carried out by numerous laboratories for many years, general agreement has not been reached on a single method or for the value of this test. Available data indicate that in spite of certain difficulties, reliable comparisons can be obtained using relatively small numbers of donors. Indeed, a difference in platelet survival of as little as 10 percent can be detected by using eight donors, whereas only four donors are required if one wishes to detect a 20 percent change. Should studies be done using donors preselected according to strict criteria of age, sex, health, etc.? It might be that less scatter among the data points would be observed and perhaps even fewer donors would be required to obtain significant values. In surveying the available information, it is clear that many investigators do have data on normal controls which could be extracted and analyzed to provide an answer to this question. Such information would be of great value in determining the criteria for selection of donors for autologous platelet survival studies.

Acute Disease↗
PubMedDate not supplied

A simple method for preparing neocyte-enriched leukocyte-poor blood for transfusion-dependent patients.

Recent treatment for patients with thalassemia and chronic anemia involves transfusion of young red cells (YRBCs) or "neocytes." We developed a technique enabling YRBCs to be separated based on their buoyant density in autologous plasma during centrifugation. Following this procedure, measurement of pyruvate kinase (PK), an age-dependent red cell enzyme, showed neocyte enrichment in the top one-third of the RBC layer corresponding to a mean of 47.5 percent of the total PK present in the unfractionated unit. To provide a neocyte transfusion preparation with an acceptable hemoglobin content, the top one-third fraction from each of three bags of blood was pooled. Leukocytes were removed from this "neocyte unit" by an initial sedimentation with 6 percent hydroxyethyl starch (HES) followed by filtration through a filter (IG 500, Imugard). This process resulted in removal of 99.3 +/- 0.5 percent (mean +/- SD) of the leukocytes with a mean RBC recovery of 89.5 +/- 5.5 percent and a final hemoglobin content of 53.4 +/- 2.3 g. Tests for plasma-free hemoglobin and HES in the supernatant of the final transfusion product gave acceptable mean values of 28 mg per dl and 3.0 mg per ml. Autologous mean RBC survival of Cr51-labeled YRBC fractions was 41.8 +/- 2.9 days (n = 5). This technique yields neocyte enrichment superior to that achieved using a cell processor (model 2991, IBM) and has the added advantage of being less costly to prepare ($45.00 [1984] U.S. per YRBC unit as compared to an estimated $135.00 [1984] U.S., IBM) and more economical in terms of blood use.

Anemia↗
PubMedDate not supplied

Plasma collection using an automated membrane device.

A plasmapheresis device with both membrane filtration and centrifugation features was tested. The device permits the collection of 500 ml of plasma within 30 minutes; when run at a 1:12.5 ratio with acid-citrate-dextrose (ACD-A) the resultant plasma factor VIII levels were 1.05 units per ml and the albumin was 41 g per l. Free hemoglobin was not detected, and there was no evidence of fibrinopeptide A, prekallikrein, or activation of complement. The plasma had a zero hematocrit value and contained few platelets and white cells. Before and after the procedure, donors and aliquots from the return line did not show any significant effect on cell count or function. This device functioned well to collect plasma for infusion or fractionation and was accepted well by donors. A major advantage is the relatively low cost for the software package ($15.00, US, 1985), which should make plasmapheresis with this device economically feasible.

Automation↗
PubMedDate not supplied

Platelet storage. Effects of leachable materials on morphology and function.

A polyolefin plastic (PL 732) bag formulated without liquid plasticizer allows storage of platelets for 5 and, now, up to 7 days. In order to assess the leaching of compounds from this new plastic, extracts of the supernatant from platelet concentrates stored in these bags were analyzed by high-performance liquid chromatography, mass spectrometry, and gas-liquid chromatography. A leachable material was detected and identified as di(2-ethylhexyl) phthalate (DEHP). During the sterilization process, migration of the DEHP occurs from the polyvinylchloride (PVC) bags into the PL 732 plastic bag. The level of DEHP was 12-fold less in the extracts of PC supernatant stored in the PL 732 bag than those in the polyvinyl chloride (PL 146) plastic bags which were used previously for platelet storage. Platelets stored in low DEHP concentrations in the PL 732 bags were composed of 10 to 35 percent of unclassifiable shapes. These shape changes were not observed in higher concentrations of plasticizer, although the morphology scores decreased during storage in PL 146 as well. This effect on morphology was not related directly to the dose of DEHP. When platelet membranes were isolated from platelets stored in the presence of radiolabeled DEHP, the amount of bound 14C-DEHP was found to be directly proportional to the concentration of DEHP in the plasma supernatant. However, while there was a linear relationship between the protein concentration in the membrane fraction and the amount of bound DEHP, no specific DEHP binding site could be identified by electrophoresis of the solubilized platelet membranes.

Blood Platelets↗
PubMedDate not supplied

Storage of human platelet concentrates in an artificial medium without dextrose.

It was shown previously that human blood platelets stored in an artificial medium (PCD) for up to 5 days remain functional in vitro and have normal survival and recovery in vivo. This report demonstrates that the medium can be simplified further by the removal of dextrose, leaving for study a medium consisting simply of balanced salts and citrate anticoagulant (PC). Some dextrose, 3.2 mM, was present in the fresh PC platelet concentrates due to plasma carryover in the production of platelet concentrates, but this dextrose concentration was considerably less than the 22.6 to 25.5 mM present in platelet concentrates in PCD or plasma. Platelet count, pH, PCO2, and PO2, as well as platelet aggregation and release responses to stimulation, in vitro, were as well preserved in the PCD or PC media as in the plasma controls. In the PC medium, platelets consumed 2.5 mM dextrose over 5 days and left 0.7 mM dextrose. The same consumption of dextrose was noted in PCD platelet concentrates, while platelets in plasma metabolized twice as much dextrose and formed twice as much lactate. Thus, the rate of glycolysis in platelet concentrates was independent of the dextrose concentration in the medium, and the platelet functions were well preserved.

Ammonia↗
PubMedDate not supplied

Effect of citrate anticoagulants on factor VIII levels in plasma.

The citrate anticoagulants used during blood collection have been developed for their benefits to red cells. The concentrations in which they are used are strictly regulated in the United States: citrate-phosphate-dextrose-adenine (CPDA) is used in a 1:8 ratio for the collection of whole blood, whereas 4 percent sodium citrate (NaCit) is used in a 1:10 ratio for manual plasmapheresis. Acid-citrate-dextrose formula A (ACD-A) or formula B (ACD-B) and NaCit are commonly used in a 1:12 or 1:15 ratio during automated plasmapheresis. These anticoagulants have different initial and final pH values and citrate concentrations and different effects on the recovery of factor VIII (FVIII) in the plasma. NaCit has a higher initial pH (6.64) than ACD-A (4.98), ACD-B (5.60), or CPDA (5.12). The effects of these different anticoagulants on plasma constituents obtained from six healthy subjects were studied. In standard citrate concentrations, the FVIII level was significantly lower (p less than 0.05) in the NaCit used for manual plasmapheresis than in either of the ACD solutions used in automated plasmapheresis (104 U/dl vs. 153 and 160 U/dl). When various ratios of NaCit to blood were used, the pH increased from 7.62 at a 1:10 dilution to 7.65 at a 1:50 dilution. As expected, a progressive decrease in anticoagulant level was associated with an increase in ionized calcium and also in the level of FVIII, with the latter values rising from 104 U per dl at 1:10 to 137 at 1:20 and 148 U per dl at 1:30. Clot formation was detected only at a ratio of 1:35.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine↗
PubMedDate not supplied

Comparative study of the efficacy and safety of intranasal DDAVP administered to normal blood donors.

A study of the efficacy and safety of intranasal 1-deamino-8-D-arginine vasopressin (DDAVP; 300 micrograms) in normal blood donors was carried out in a double-blind, controlled, comparative study. In addition, the effect of heparin or citrate anticoagulation of blood on the recovery of factor VIII (FVIII) in plasma, cryoprecipitate, and a FVIII concentrate was assessed. Citrated plasma from placebo (CP) or DDAVP-treated donors (CD) contained 1103 +/- 73 and 1470 +/- 141 units per liter of FVIII, respectively (p less than 0.01), whereas the heparinized plasma from placebo (HP) or DDAVP-treated donors (HD) contained 1328 +/- 130 (p less than 0.01) and 2023 +/- 358 units per liter (p less than 0.01), respectively. The FVIII could be recovered in both cryoprecipitate and cold-reprecipitated cryoprecipitate (CRC) fractions. DDAVP treatment improved FVIII recovery by 41 percent in the concentrate from citrated plasma (p less than 0.01) and by 127 percent in that from heparinized plasma (p less than 0.01). The specific activity of concentrates from the CP, CD, HP, and HD groups was 0.95 +/- 0.1, 1.4 +/- 0.1 (p less than 0.01), 0.9 +/- 0.1, and 1.47 +/- 0.2 U per mg of protein (p less than 0.01), respectively. The stability of the final product was the same, regardless of the method of treatment or collection. The side effects of intranasal treatment were mild and transient and occurred with similar frequency in both placebo and DDAVP treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Intranasal↗
PubMedDate not supplied

The effects of irradiation on platelet function.

Current medical practice involves the irradiation of blood components, including platelet concentrates, before their administration to patients with severe immunosuppression. The authors studied the effect of irradiation on in vitro platelet function and the leaching of plasticizers from the bag, both immediately and after 5 days of storage. The platelet count, white cell count, pH, glucose, lactate, platelet aggregation and release reaction, and serotonin uptake were not altered by the irradiation of random-donor or apheresis units with 2000 rads carried out at 0 and 24 hours and 5 days after collection. The leaching of di(2-ethylhexyl)phthalate from the plastic bags followed by the conversion to mono(2-ethylhexyl)phthalate was not increased by irradiation. Therefore, it is possible to irradiate platelet concentrates on the day of collection and subsequently store them for at least 5 days while maintaining in vitro function. This procedure could have considerable benefit for blood banks involved in the provision of many platelet products.

Blood Platelets↗
PubMedDate not supplied

Metabolism and tissue distribution of mono-2-ethylhexyl phthalate in the rat.

The absorption, distribution and metabolic excretion of mono-2-ethylhexyl [7-14C]phthalate (MEHP) were studied in the rat. This compound was readily absorbed from the gastrointestinal tract. Radioactivity following intravenous administration of 14C-MEHP was rapidly distributed in all tissues, with the highest levels occurring in the liver, kidney, and urinary bladder. Excretion of radioactivity was rapid and approximately 80% of the dose was eliminated 24 hr after oral administration, 72% in the urine and 8% in feces. MEHP was extensively metabolized after oral administration, and the major urinary metabolites were identified as an alcohol, a ketone, and an acid resulting from the side-chain oxidation of MEHP. A trace of o-phthalic acid was also identified.

Animals↗