Genetics of platelet reactivity in normal, healthy individuals.

BACKGROUND: The Platelet Function Analyzer-100 (PFA-100) is widely used to measure platelet reactivity in whole blood under high shear. OBJECTIVE: To characterize the genetic component of platelet reactivity among normal individuals, using the PFA-100. METHODS: We compared baseline platelet reactivity with sex, age, platelet count, hematocrit, plasma von Willebrand factor antigen (VWF:Ag), and alleles of seven candidate genes: integrin subunits alpha2 (ITGA2) and beta3 (ITGB3), platelet glycoproteins GPIbalpha (GP1BA) and GPVI (GP6), purinogenic receptors (P2RY1 and P2RY12) and cyclooxygenase-1 (COX1). RESULTS: Based on linear and logistic regression models, we report an inverse correlation between baseline closure time (CT) initiated by collagen plus epinephrine (CEPI) and plasma VWF:Ag level, ITGA2 807T and P2RY1 893C, and an inverse correlation between baseline CT initiated by collagen plus adenosine diphosphate (CADP) and P2RY1 893C or GP1BA -5C. CONCLUSIONS: These results indicate that genetic polymorphisms in ITGA2 and P2RY1 combine with plasma VWF:Ag levels to modulate baseline platelet reactivity in response to collagen plus EPI, while genetic differences in P2RY1 and GP1BA significantly effect platelet responses to collagen plus ADP. Our results demonstrate that the PFA-100 can be used to evaluate the effects of genetic predictors of platelet function.

Individualization of bypassing agent treatment for haemophilic patients with inhibitors utilizing thromboelastography.

The treatment of bleeding for haemophilic patients with inhibitors relies on the use of the bypassing agents, recombinant factor VIIa and factor eight inhibitor bypass activity (FEIBA). While both therapies are effective in the majority of bleeding episodes, there is a significant amount of interindividual variability when it comes to the response to therapy. As of yet, there is no reliable laboratory parameter that can predict the response to therapy in the same manner that factor VIII and factor IX levels predict response in non-inhibitor patients. Developing such a laboratory parameter is vital in order to maximize the clinical efficacy of these agents. Thromboelastography (TEG) is a device, which assesses clot formation over time in whole blood and has several characteristics which suggest it may be an effective way to monitor bypass agent therapy. We studied the ability of TEG to individualize the treatment regimens of three patients with high titre inhibitors assessing the response to recombinant factor VIIa, FEIBA, and when both were used sequentially. The TEG allowed for individualization of treatment for each of the three patients and resulted in more effective, convenient and less expensive treatment regimens. We thus believe that TEG is a promising device for monitoring of bypass agent therapy and should be studied further.

The mode of action of cervinomycin in Staphylococcus aureus.

The mode of action of cervinomycin, which is a new antibiotic active against Gram-positive bacteria including anaerobes, was studied in Staphylococcus aureus using triacetylcervinomycin A1 (ACVM), an acetyl derivative of cervinomycin A1. ACVM inhibited strongly the growth of the organism when it was added to a culture at the time of inoculation at a concentration of 1.0 micrograms/ml, but did not inhibit when added to a logarithmic phase culture even at 10.0 micrograms/ml. The antibiotic also inhibited the incorporation of labeled precursors of cell wall peptidoglycan (N-acetylglucosamine), RNA (uridine), DNA (thymidine) and protein (L-leucine) into both whole cell and acid-insoluble macromolecular fractions. ACVM stimulated the leakage of UV260-absorbing materials, amino acids and potassium ions from resting cells and protoplasts. Phospholipids partially reversed the inhibitory activity of ACVM in a growing culture. These findings suggest that ACVM interact with phospholipids in the cytoplasmic membrane and then interfere with the membrane transport system.

Izupeptins A and B, new glycopeptide antibiotics produced by an actinomycete.

In the course of screening for new high molecular weight peptidoglycan synthesis inhibitors, izupeptins A and B, antibiotics active against Gram-positive bacteria including methicillin-resistant Staphylococci and Clostridium were discovered. The antibiotics were found to be new members of the glycopeptide antibiotic family, namely of the vancomycin type, based on chemical and spectroscopic data. The molecular weight of izupeptin A was determined to be 1,475 by SI (secondary ion)-MS (integer molecular weight, 1,473), and it contains two chlorine atoms.

The site of inhibition of bacterial cell wall peptidoglycan synthesis by azureomycin B, a new antibiotic.

Azureomycin B (10 micrograms/ml), a new antibiotic from Pseudonocardia azurea nov. sp., caused the accumulation of lipid intermediate and inhibition of peptidoglycan synthesis in an invitro system using a particulate fraction from Bacillus megaterium KM with UDP-MurNAc-[3H]pentapeptide and cold UDP-GlcNac or cold UDP-MurNAc-pentapeptide and UDP-[3H]GlcNAc as substrates. At higher concentrations of azureomycin B (over 100 microgram/ml), lipid intermediate accumulation was also inhibited. When particulate fraction from Escherichia coli Y-10 and UDP-[14C[GlcNAc and cold UDP-MurNAc-pentapeptide were used, accumulation of lipid intermediate and inhibition of peptidoglycan synthesis were also observed. These results indicate that the primary target of azureomycin B is the transfer of the disaccharide peptide unit (GlcNAc-MurNAc-pentapeptide) from lipid-bound precursor to acceptor.

Studies on bacterial cell wall inhibitors. VIII. Mode of action of a new antibiotic, azureomycin B, in Bacillus cereus T.

Azureomycin B, a new antibiotic which contains sugar, amino acid and phenol moieties and inhibits Gram-positive bacteria, was found to be a specific inhibitor of peptidoglycan synthesis in bacteria. The antibiotic lysed growing cells of Bacillus cereus T at a concentration of 10 micrograms/ml but did not affect resting cells. Microscopical observation revealed swelling and lysis of the bacterial rods when treated with azureomycin B. The incorporation of [3H]diaminopimelic acid or [14C]glucosamine into acid-insoluble fraction of growing cells of Bacillus cereus T was strongly inhibited in the presence of azureomycin B, but that of [14C]leucine, [3H]thymidine or [3H]uridine were not, at least until 5 minutes after the beginning of the incubation. The antibiotic caused accumulation of a nucleotide precursor in the cells which was identified as UDP-MurNAc-L-Ala-D-Glu-meso-Dpm-D-Ala-D-Ala. Thus the site of action was suggested to lie between this nucleotide and peptidoglycan in the pathway of peptidoglycan synthesis.

Studies on bacterial cell wall inhibitors. VII. Azureomycins A and B, new antibiotics produced by Pseudonocardia azurea nov. sp. Taxonomy of the producing organism, isolation, characterization and biological properties.

Two new basic water-soluble antibiotics, azureomycins A and B, were isolated from the culture broth of an actinomycete, strain AM-3696, designated as Pseudonocardia azurea nov. sp. The antibiotics exhibit moderate antimicrobial activities against Gram-positive bacteria including penicillin-resistant Staphylococcus, Mycobacterium and Clostridium. They inhibit the synthesis of bacterial cell wall peptidoglycan.

Comparison of filtering efficiency of four new in-line blood transfusion filters.

Efficient removal of debris from stored human blood prior to transfusion has become increasingly important. The debris, consisting largely of microaggregates of platelets and fibrin, is not effectively removed by passage through a standard transfusion filter. This study evaluated the performance of four of the currently available small pore in-line blood transfusion filters. Filters tested included the Bentley PF-127, the Pall Ultipor SQ-40, the Swank In-Line IL-200 and the Fenwal Microaggregate Blood Filter. A standard blood administration filter was also tested, the McGraw V-2950. The rate of blood flow through the filters was recorded using single and multiple units of blood. The screen filtration pressure and debris weight of the filtered blood were studied to compare effectiveness of filtration. The Swank filter was effective in debris removal and maintained good flow rates. The Bentley and Fenwall filters removed debris nearly as well, but had reduction of flow rates after smaller infusions. The Pall filter maintained high flow rates but did not remove debris as effectively, particularly with pressure infusion. The standard 170 mu pore blood transfusion filter does not remove microaggregates.