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Biomedical subjects

V Hornsey

Publications and source records attributed to V Hornsey.

10 recordsLinked to original sources
PubMed2004

Platelet storage solution affects on the accuracy of laboratory tests for platelet function: a multi-laboratory study.

BACKGROUND AND OBJECTIVES: Extent of shape change (ESC) and hypotonic shock response (HSR) have been widely used to characterize the in vitro function of platelets and have been shown to correlate with in vivo viability. These assays have been routinely performed using platelet-poor plasma (PPP) as the test sample diluent. Because of the increasing popularity of storing platelets in synthetic media, it is important to understand the effects of using these synthetic media as test diluents for ESC and HSR measurements. The objective of this study was to determine the effect of using platelet storage solutions vs. plasma for the in vitro testing of ESC and HSR. MATERIALS AND METHODS: Six laboratories participated in this study. Platelets were prepared by apheresis, the platelet-rich plasma (PRP) method, or derived from buffy-coats. Each platelet preparation was divided, half being stored in plasma and the other half in storage solution. ESC and HSR testing were performed in duplicate on days 1 and 5, using each of three diluents: autologous plasma; fresh-frozen plasma; or storage solution. RESULTS: For both ESC and HSR, dilutions made in each of the three diluents yielded significantly different results. Dilutions made in storage solutions were more than 30% lower for ESC and HSR than those made in autologous plasma (P < 0.0001). Dilutions made in thawed fresh-frozen plasma were more than 16% lower for ESC and HSR than those made in liquid autologous plasma (P < 0.0005). CONCLUSIONS: ESC and HSR test results are significantly affected by the test diluent. Platelets should be diluted in plasma (preferably autologous) for the in vitro testing of ESC and HSR, regardless of the media in which they are stored.

Blood Platelets↗
PubMed1999

Application of a time-resolved fluoroimmunoassay for the analysis of normal prion protein in human blood and its components.

BACKGROUND AND OBJECTIVES: To quantify the cellular isoform of prion protein (PrP(c)) in human blood using a new time-resolved dissociation-enhanced fluoroimmunoassay (DELFIA). MATERIALS AND METHODS: The DELFIA was optimised for human blood samples and applied to isolated cell and plasma fractions from blood donations. The physicochemical properties of PrP(c) were analysed. RESULTS: 26. 5% of blood PrP(c) was associated with the platelet fraction, 0.8% with polymorphonuclear leucocytes, 2.4% with mononuclear leucocytes, 1.8% with red cells and 68.5% with plasma (mean values from 4 processed donations). CONCLUSION: The majority of blood PrP(c) is found in the platelet and plasma compartments.

Antigens↗
PubMed1990

High-level expression of biologically active human alpha 1-antitrypsin in the milk of transgenic mice.

Reduced circulating levels of alpha 1-antitrypsin (alpha 1 AT) are associated with certain alpha 1 AT genotypes and increased susceptibility to emphysema. Unfortunately, the amounts of alpha 1 AT that would be required for replacement therapy are beyond the capacity of plasma fractionation and mammalian cell culture systems. Thus, we have examined the potential of transgenic animals as an alternative means of producing human alpha 1 AT. A hybrid gene constructed by using sequences from the ovine milk protein gene beta-lactoglobulin fused to an alpha 1 AT "minigene" was used to generate transgenic mice. Of 13 independent transgenic mice and mouse lines, 5 expressed the hybrid gene in the mammary gland, 5 in the salivary glands, and 2 in both these tissues. Human alpha 1 AT was secreted into the milk of each of the 7 mice and mouse lines that expressed the hybrid gene in the mammary gland. Four of these mammary-expressing transgenic mice and mouse lines produced concentrations of at least 0.5 mg of alpha 1 AT per ml in their milk; one line (AATB 35) produced 7 mg of this protein per ml. alpha 1 AT from transgenic mouse milk was similar in size to human plasma-derived alpha 1 AT and showed a similar capacity to inhibit trypsin. Expression at equivalent levels in transgenic sheep or cattle would yield sufficient alpha 1 AT for therapeutic purposes.

Animals↗
PubMed1989

Human atrial natriuretic factor (ANF). Characterisation of a monoclonal antibody panel and its use in radioimmunoassay.

The production of nine monoclonal antibodies to human atrial natriuretic factor (ANF 1-28) is described. All possible combinations of two antibodies failed to reveal any which could simultaneously bind ANF. Studies with ANF analogues and the antibodies having the three highest affinity values (KD = 5, 25 and 21 pM) indicated that the antibodies are directed to the central portion of the antigen molecule. The highest affinity antibody was able to replace polyclonal antisera in the radioimmunoassay of ANF in extracts of plasma.

Antibodies, Monoclonal↗
PubMed1988

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.

Amino Acids↗
PubMed1986

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).

Factor VIII↗
PubMed1985

Enhancement of factor VIII-von Willebrand factor ristocetin cofactor activity by monoclonal antibodies.

Five monoclonal antibodies to human von Willebrand factor were selected for characterization from 18 produced in murine hybridomas. All showed a high and specific affinity for human von Willebrand factor (vWf) but exhibited little if any cross-reaction with sera from other species. The antibodies defined four epitopes on vWf, none of which were involved in platelet binding. Binding of two distinct antibodies at one of these epitopes was associated with enhancement of the rate of vWf-dependent platelet agglutination in the presence of ristocetin. This effect was more noticeable when cryosupernatant plasma was used in place of normal plasma as the source of vWf, and was not explicable simply in terms of antibody-induced cross-linking of vWf.

Animals↗
PubMed1982

A comparison of acylated streptokinase-plasminogen complex and streptokinase in healthy volunteers.

The in vivo effects on the fibrinolytic and coagulation system of infusion acylated streptokinase-plasminogen complex (BRL 26921; 5, 7 and 12 mg) or streptokinase (250,000 u) were determined in healthy male volunteers. While this dose of streptokinase resulted in depletion of plasminogen and antiplasmin, and in some cases of fibrinogen and coagulation factors V and VIII, the equivalent 7 mg dose of BRL 26921 had little effect on these parameters. 12 mg BRL 26921 had some systemic effects on the fibrinolytic system. For initial clinical studies a dose of 10 mg BRL 26021 would seem appropriate. Both drugs induced an anamnestic rise in streptokinase antibody, whereas no change in liver function tests were observed. A delayed mild febrile reaction was observed in some subjects following infusion of streptokinase or BRL 26921. Clinical, laboratory, and subjective monitoring revealed no other adverse effects with either drug.

Adult↗