Artificial factor VIII deficient plasma: preparation using monoclonal antibodies and its use in one stage coagulation assays.

Monoclonal antibodies to factor VIII antigen (VIII:Ag) and von Willebrand factor (vWf:Ag) were immobilised on Sephacryl S-1000 and tested for their ability to deplete normal human citrated plasma of factor VIII. A combination of two antibodies to VIII:Ag and one antibody to vWf:Ag was required to produce plasma containing less than 0.01 IU/ml. Its performance in the one stage coagulation assay of VIII:C was equivalent to that of congenital VIII deficient plasma for the assay of normal and haemophilic plasma and factor VIII concentrates. Storage of freeze dried aliquots of this product at -20 degrees C, +4 degrees C, and 37 degrees C showed that it could be used as a substrate for at least six months when stored at temperatures +4 degrees C and below.     

The prevalence of Gilles de la Tourette syndrome in children and adolescents with autism: a large scale study

BACKGROUND: An earlier small-scale study of children with autism revealed that 8.1% of such patients were co-morbid for Gilles de la Tourette syndrome (GTS). The present study is a large scale test of whether this result replicates. METHOD: Four hundred and forty-seven pupils from nine schools for children and adolescents with autism were screened for the presence of motor and vocal tics. RESULTS: Subsequent family interviews confirmed the co-morbid diagnosis of definite GTS in 19 children, giving a prevalence rate of 4.3%. A further 10 children were diagnosed with probable GTS (2.2%). CONCLUSIONS: These results indicate that the rate of GTS in autism exceeds that expected by chance, and the combined rate (6.5%) is similar to the rates found in the smaller-scale study. Methodological considerations and alternative explanations for an increased prevalence are discussed.     

In vitro activity of daptomycin in combination with low-dose colistin against a diverse collection of Gram-negative bacterial pathogens

The activity of colistin in combination with daptomycin was assessed using 30 Gram-negative type strains and multidrug-resistant isolates with defined mechanisms of resistance. Daptomycin minimum inhibitory concentrations (MICs) were determined with and without sub-inhibitory concentrations of colistin. The activity of daptomycin was not affected with respect to Escherichia coli, Klebsiella pneumoniae or Pseudomonas aeruginosa. For colistin-susceptible Acinetobacter baumannii, sensitisation factors ranged from 8 to 128 (median 32), with the daptomycin MIC being reduced to the Clinical and Laboratory Standards Institute (CLSI) enterococci susceptibility breakpoint of 4 μg/ml for the ATCC 19606 type strain. A combination of daptomycin and colistin may be useful for the treatment of A. baumannii but not infections due to other Gram-negative species.     

Room Temperature, Microtray Chromogenic Assay of Factor VIII:C

Commercial reagents of non-human origin were used to provide a room temperature, microtray chromogenic assay for factor VIII. The assay allows determination of factor VIII in the range 15-150% of normal plasma levels with a coefficient of variation of 3-4%. Haemophilic plasmas and factor VIII concentrates may also be assayed by varying the pre-dilution step. A good correlation was demonstrated with results obtained using an established one-stage clotting assay (r = 0.9985).     

Stored red‐blood‐cells inhibit platelet function under physiologic flow

Background and Objectives The DiaMed Impact R tests platelet function under close to physiological flow conditions. The machine is designed to use whole blood but by adding back compatible red cells, it can be used to study stored platelet concentrates. To date, red cells ≤14 days old have been used. In this study, the effect on the assay of using red cells stored for up to 60 days was examined. Material and Methods This study looked at buffy coat‐derived platelet concentrates on day 2 of storage along with various stored red‐blood‐cells (RBC). To determine whether the age of the RBC is a factor in supporting adhesion and aggregation, platelets were assayed with either RBC stored between 2 and 60 days or with separated ‘young’ and ‘old’ red cell populations obtained using a centrifugation method and confirmed by percoll gradient analysis. Results A statistically significant difference was observed between red‐blood‐cells stored for ≤20 days compared with those which have been stored for 21–60 days in respect of their ability to support platelet adhesion (SC) and aggregation (AS) (P < 0·01). Separating red cells by centrifugation into top (young population) and bottom (old population) showed that the effect of storage was much greater than was any difference between young and old at the individual time‐points e.g. ‘young’ red cells from stored units were poorer at supporting platelet adhesion and aggregation than ‘young’ red cells from fresh units. Conclusion Results suggest that the red cells should be stored for less than 21 days when using this assay. This assay may also allow assessment of red cell functionality.     

Platelet storage in Fresenius/NPBI polyolefin and BTHC-PVC bags: a direct comparison

SUMMARY: New platelet storage systems, such as changes in the plastic of the storage bags, require validation. In this study, pooled buffy coat platelets stored in Fresenius/NPBI polyolefin bags were compared with those stored in Fresenius/NPBI butyryl-trihexyl citrate (BTHC) plasticized polyvinyl chloride (PVC). The CompoSelect thrombocyte polishing filter system (1000 mL polyolefin bag) and the CompoStop F730 system (1300 mL BTHC-PVC bag) were used to prepare paired, plasma-suspended, buffy coat platelet concentrates. Samples were taken up to day 7 for in vitro analysis. In a separate experiment, 12 units were prepared using the CompoStop F730 system and samples taken after leucofiltration for FXIIa assay. By day 7, platelet concentrates stored in BTHC-PVC demonstrated significantly higher pH levels (7.32 +/- 0.05 vs. 7.26 +/- 0.05) and a greater degree of cell lysis as shown by increased lactate dehydrogenase levels (497 +/- 107 vs. 392 +/- 81 U L(-1)). The supernatants contained higher concentrations of soluble P-selectin and the chemokine 'regulated on activation, normal T-cell expressed and presumably secreted', which are released from the alpha-granules during activation. The ATP concentrations were significantly lower in BTHC-PVC. Platelet counts, mean platelet volume and hypotonic shock response were similar for both bags. FXIIa antigen concentrations were 0.6 +/- 0.2 ng mL(-1) indicating that activation of the contact factor pathway had not occurred. Although the CompoStop F730 leucoreduction filter did not activate the contact system, platelets stored in 100% plasma in BTHC-PVC bags demonstrated different in vitro characteristics from those stored in polyolefin. Further work is required to demonstrate whether these differences will affect in vivo recovery and survival.     

The interaction of von Willebrand factor (vWf) with collagen: investigation of vWf-binding sites in the collagen molecule

Following fragmentation of the collagen molecule, we have examined the ability of the isolated fragments to bind vWf. In view of the importance of collagen tertiary and quaternary structure for binding, fragments were first renatured to restore triple-helical conformation and then polymerized. Results indicate the presence of specific vWf-binding sites in both the alpha 1(I)- and alpha 2(I)-chains of type I collagen. Cleavage of the alpha 1(I)-chain with cyanogen bromide suggests the presence of at least four (conceivably several more) binding sites implying a wide distribution of sites along the length of the collagen type I molecule. Collagen type III appears to possess a similar wide distribution of sites. Chemical modification of specific amino acid residues indicates that interaction involves arginyl residues in collagen and carboxyl groups in vWf. Although interaction between fibronectin and collagen fibres also involves collagen arginyl residues and carboxyl groups in fibronectin (authors' unpublished results), fibronectin does not compete with vWf in the binding to collagen fibres.     

The relationship between fractionation and total dose for X ray induced brain damage

An isoeffect curve for X ray induced brain damage in the rat has been obtained by comparing the effects of fractionation of dose into 8,15 or 30 equal fractions given in the same overall treatment time of 6 weeks. The slope of the isoetfect curve is 0.37. This data on the brain is compared with other published data for radiation damage to the rat spinal cord and a composite isoeffect curve for damage to the central nervous system (CNS) is shown. From this we suggest a modified formula for the CNS that is in agreement with that suggested by van der Kogel⁷ for the spinal cord, and is more compatible with present clinical experience than the normal Ellis formula.     

Insulin and glucagon-like immunoreactivity in the river lamprey (Lampetra fluviatilis).

Recently it has been established that the islet tissue of the river lamprey secretes insulin. These studies were aimed at determining serum levels of insulin-like immunoreactivity after isletectomy, glucose loading, and adrenaline treatment of adult river lampreys. Comparison of human insulin standard curves with lamprey islet tissue dilution curves indicates that the two curves have significantly different slopes. Although quantification of insulin in lamprey serum was therefore not possible, differences between control and experimental groups can be tested for by hierarchical analysis of variance. The insulin concentration in the serum of totally isletectomized animals is significantly lower than that of sham-operated controls. Two hours after a single injection (100 mg) of glucose there was no significant difference in insulin concentration as compared with saline-injected controls, but 8 and 24 hr after such injection insulin levels were significantly elevated. After long-term glucose loading (100 mg of glucose twice daily for 12 days) serum levels of insulin were significantly elevated. Insulin levels in adrenaline-treated animals (0.1 mg twice daily for 3 days) were significantly lower than in saline-injected controls. Glucagon-like immunoreactivity was found in both extracts of the intestine and the cranial islet tissue. These studies indicate the significant role of insulin in the control of carbohydrate metabolism in the river lamprey during the fasting stage of its life cycle.