Biomedical subjects

S J Wagner

Publications and source records attributed to S J Wagner.

42 records · Page 3Linked to original sources

PubMed1979

Gallium-68 labeling of albumin and albumin microspheres.

Because of the high stability constant of gallium transferrin, the formation of a protein that will be stable in vivo and labeled with gallium-68 (a positron emitter) requires preliminary coupling of a strong chelating group to the protein. In the present study, we have used a reaction developed by Krejcarek and Tucker, in which DTPA is coupled to proteins by the formation of an amide bond. Using human serum albumin (HSA) as a model, we have studied the efficiency of the reaction of HSA with the mixed acid anhydride of the quarternary triethyl ammonium salt of DTPA and butyl formate, as a function of the ratio of albumin to DTPA. After purification of the DTPA-labeled HSA, it is possible to prepare Ga-68-labeled albumin in high yield by chelation of the Ga-68 with the DTPA-labeled protein. In vitro and in vivo stability studies showed that the labeled protein was stable over a period of several hours. The same type of bifunctional chelate has been used to attach Ga-68 to HSA microspheres.

Animals↗

PubMedDate not supplied

Quantification of juvenile hormone III, vitellogenin, and vitellogenin-mRNA during the oviposition cycle of the lubber grasshopper.

The vitellogenic cycle of the lubber grasshopper (Romalea microptera) was studied by measuring levels of juvenile hormone (JH III), vitellogenin, and vitellogenin-mRNA through the first oviposition cycle. JH III and vitellogenin were measured by radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA), respectively. To measure vitellogenin-mRNA, a partial (753 bp) cDNA fragment of vitellogenin was isolated from the fat body of vitellogenic animals. The sequence of this cDNA was related to vitellogenin sequences in other insect species. Using these sequence data, an RT-PCR (reverse transcriptase polymerase chain reaction) assay was developed to quantify vitellogenin-mRNA levels during the oviposition cycle. Vitellogenin-mRNA levels in the fat body tissue from virgin females were measured on specific days after eclosion and compared to hemolymph levels of JH III and vitellogenin from the same individuals. The levels of all three compounds (JH III, vitellogenin, and vitellogenin-mRNA) showed similar changes throughout the oviposition cycle, being undetectable or nearly undetectable initially (day 3), rising to maximum levels on days 23 and 28, and then dropped to lower or undetectable levels on the day of oviposition. The ability to measure these characteristics will be useful for studying the effects of hormonal and nutritional manipulations on reproduction.

Animals↗

PubMedDate not supplied

Bacteria levels in components prepared from deliberately inoculated whole blood held for 8 or 24 hours at 20 to 24 degrees C.

BACKGROUND: An increase from 8 to 24 hours in the time that units of whole blood can be held at room temperature after phlebotomy would give blood centers more flexibility in component manufacturing and might allow receipt of many infectious disease test results prior to component preparation. However, the potential for bacterial growth during prolonged holding periods requires further study. STUDY DESIGN AND METHODS: In the Phase I study, 2-unit pools of ABO-identical whole blood were deliberately inoculated on Day 0 with Staphylococcus aureus or Pseudomonas fluorescens. They were then divided in half and stored at 20 to 24 degrees C. Red cells (RBCs) with additive solution, platelet concentrates (PCs), and frozen plasma were prepared after 8 and 24 hours. Bacteria levels in PCs and RBCs were monitored on Day 1; bacteria levels were measured in plasma after thawing. In the Phase II study, the same basic design as in Phase I was used, except that 10 bacterial species were studied, lower inocula were used, and RBCs prepared after a 24-hour room-temperature whole-blood hold were white cell-reduced by filtration. Bacterial growth was monitored during 42-day storage of RBCs (1 - 6 degrees C) and 5-day storage of PCs (20 - 24 degrees C) and after thawing of frozen plasma. RESULTS: For Phase I, significantly higher bacteria levels were observed in RBCs prepared after a prolonged hold (p < 0.05); higher levels were not observed in PCs and thawed plasma units. In Phase II, prior to white cell reduction by filtration, 8 of 10 organisms had significantly higher levels in RBCs prepared after a 24-hour hold than in RBCs prepared after an 8-hour hold, when both were examined on Day 1 (p < 0.05). For seven of eight organisms examined on Days 1, 21, and 42, filtration (white cell reduction) reduced the bacteria in RBCs prepared from 24-hour whole blood units to those levels found in unfiltered RBCs prepared from whole blood units held at 8 hours. A prolongation of the holding time from 8 to 24 hours resulted in significantly lower bacteria levels (p < 0.05) in PCs early in storage (Days 1, 1 - 2, or 1 - 3) for seven organisms, with no significant difference for two organisms, and a small but significant increase for one organism (Day 3, p < 0.05). There was no difference in bacteria or endotoxin levels in thawed units of plasma prepared from whole blood after 8- or 24-hour holding times. CONCLUSION: The levels of bacteria present in components after deliberately inoculated whole blood units are held for 8 and 24 hours depended on the organisms tested, the whole-blood holding period, and the blood component assayed; for RBCs, they also depended on whether WBC reduction by filtration was performed.

Bacteremia↗

PubMedDate not supplied

Evaluation of swirling, pH, and glucose tests for the detection of bacterial contamination in platelet concentrates.

BACKGROUND: Although infrequent, episodes of transfusion-associated bacterial sepsis may lead to serious outcomes or death and therefore are of concern. This study evaluates the sensitivity of three surrogate tests for the presence of bacteria in platelet concentrates: cessation of swirling, low extracellular pH, and low plasma glucose levels. STUDY DESIGN AND METHODS: Day 0 platelet concentrates were inoculated with low levels of one of seven bacterial strains and stored with agitation at 20 to 24 degrees C for up to 5 days. In the morning and afternoon of each day of storage, bacterial levels were ascertained by quantitative plate culture, and platelet concentrates were tested for platelet pH, plasma glucose, and swirling. Quantitative and semiquantitative dipstick techniques were used to determine pH and glucose levels. RESULTS: Platelet concentrates had attained stationary phase growth of Streptococcus pyogenes, Staphylococcus aureus, Escherichia coli, Bacillus cereus, Enterobacter cloacae, Streptococcus mitis, or Staphylococcus epidermidis (> or = 10(7) -10(8) colony-forming units [CFU]/mL) before either the swirling or dipstick methods suggested the presence of bacteria. The sensitivity of swirling and glucose tests for detecting bacterial contamination in platelet concentrates was generally comparable. Although the sensitivity of the pH test was generally similar to that of swirling and glucose tests for most bacteria, platelet concentrates contaminated with E. cloacae had normal pH despite the presence of high levels of bacteria (> or = 10(7)-10(8) CFU/mL). CONCLUSION: The sensitivity in detection of bacteria in platelet concentrates by the swirling technique or by measuring extracellular pH or plasma glucose is less than the sensitivity reported for microscopy with Gram stain (10(5)-10(6) CFU/mL), fluorescence microscopy with acridine orange stain (10(4)-10(5) CFU/mL), chemiluminescence detection of ribosomal RNA (10(3)-10(4) CFU/mL), and automated bacterial culture (1 CFU/sample volume).

Bacteremia↗

PubMedDate not supplied

Investigation of photosensitizing dyes for pathogen reduction in red cell suspensions.

Despite recent advances in blood safety by careful donor selection and implementation of infectious disease testing, transmission of viruses, bacteria and parasites by transfusion can still rarely occur. One approach to reduce the residual risk from currently tested pathogens and to protect against the emergence of new ones is to investigate methods for pathogen inactivation. The use of photosensitizing dyes for pathogen inactivation has been studied in both red cell and platelet blood components. Optimal properties of sensitizing dyes for use in red cell suspensions include selection of dyes that traverse cell and viral membranes, bind to nucleic acids, absorb light in the red region of the spectrum, inactivate a wide range of pathogens, produce little red cell photodamage from dye not bound to nucleic acid and do not hemolyze red cells in the dark. Early research at the American Red Cross focused on the use of a class of dyes with rigid structures, such as the phenothiazine dyes, beginning with the prototypical sensitizer methylene blue. Results revealed that methylene blue phototreatment could inactivate extracellular virus, but resulted in undesirable defects in the red cell membrane that resulted in enhanced hemolysis that became evident during extended refrigerated blood storage. In addition, methylene blue phototreatment could neither inactivate intracellular viruses nor appreciably inactivate bacteria under conditions of extracellualar viral killing. Attempts to improve intracellular viral inactivation led to the investigations of more hydrophobic phenothiazines, such as methylene violet or dimethylmethylene blue. Although these dyes could inactivate intracellular virus, problems with increased red cell membrane damage and hemolysis persisted or increased. Further studies using red cell additive storage solutions containing high levels of the impermeable ion, citrate, to protect against colloidal osmotic hemolysis as well as competitive inhibitors to limit sensitizer binding to red cell membranes revealed that photoinduced hemolysis stemmed from dye bound to the red cell membrane as well as dye free in solution. Use of red cell additive solutions to prevent colloidal-osmotic hemolysis and use of novel flexible dyes that only act as sensitizers when bound to their targets are two techniques that currently are under investigation for reducing red cell damage. Ultimately, the decision to implement a photodynamic method for pathogen reduction will be determined by weighing the risks of unintended adverse consequences of the procedure itself, such as the potential for genotoxicity and allergic reactions, against the cost and benefits of its implementation.

Coloring Agents↗

PubMedDate not supplied

Reducing the infectivity of blood components--what we have learned.

The safety of the nation's blood supply has improved over the last several years as a result of more intensive donor screening and viral testing. Concurrently, there has been more judicious use of blood components. Although the risk is small, transmission of blood borne viruses, bacteria and parasites can occur. Investigators have studied a myriad of processes for pathogen depletion and/or inactivation, including the use of chemicals, extended storage, filtration, heating, irradiation, photochemicals and washing. Pasteurization, methylene blue and solvent-detergent processes have been introduced in parts of Europe for improving the safety of plasma used for transfusion. The FDA is reviewing a license application for the solvent-detergent process. For red cells, use of highly efficient leukodepletion filters is believed to be equivalent to antibody testing for the prevention of CMV disease transmission. Otherwise, no successful treatments have yet been identified for red cells or platelets. Several photochemicals, which may be useful for treating these components, are being studied. However, there appear to be trade-offs between the extent of pathogen inactivation, platelet or red cell damage, and genotoxicity. These as well as other biological parameters and operational issues will need to be further evaluated before implementation can be considered.

Blood↗