A murine monoclonal antibody 14A2.H1, raised against acute myeloid leukaemia cells, identifies a previously undescribed 27 kDa platelet surface glycoprotein which is expressed at low copy number (10(3)/platelet). MAb 14A2.H1 caused aggregation of platelets which was dependent on Fc gamma RII. Binding of the antibody to platelets was not altered by activation by thrombin or phorbol ester. In haemopoietic cell populations the antibody bound to megakaryocytes, monocytes (weakly), several myeloid leukaemic cell lines and fresh myeloid leukaemic blasts from some patients. Lymphocytes, lymphoid cell lines, neutrophils and haemopoietic progenitor cells were negative. Expression of the antigen was not restricted to haemopoietic cells as epithelial cells in tonsillar crypts and endothelial cells were positive.

Three laboratory assays for von Willebrand Factor (vWF), namely, (i) a standard "antigen" [antiseraenzyme-linked immunosorbent assay (ELISA)-based] (vWF :Ag), (ii) a standard ristocetin-dependent platelet agglutination procedure (vWF:RCof), and (iii) a newly developed ELISA-based functional vWF collagen binding assay (vWF:CBA), were coevaluated. We (a) assessed their ability to detect vWF under different assay conditions and (b) reevaluated normal vWF reference ranges using citrated plasma from >200 normal individuals. The following effective normal reference ranges were derived: vWF-Ag (40-200%), vWF:CBA (50-400%), and vWF:RCof (45-200%). Based on other laboratory data, caution is indicated in the interpretation of "borderline" or "equivocal" test results (e.g., 35-55%), since these may derive from normal individuals or from vWD patients. In addition, our study shows that selection of different assay conditions, different test plasma dilutions, or different test sample processing methods can also lead to differences in the "apparent" levels of detected vWF. For example, using plasma from 100 normal individuals processed as "test samples," we determined that higher sample dilutions tended to provide lower (dilution factor adjusted) assay results in the case of the vWF:Ag and vWF:CBA, and higher assay results in the case of the vWF.RCof, with greater differences noted in test samples containing higher levels of vWF. The explanation for these findings relate to the assay design. Thus, in the diagnostic laboratory, the standard vWF:Ag, vWF:CBA, and vWF:RCof assays procedures are designed to provide calibration curves that are "upward linear" in the (vWD) clinically important region of 0-50% of normal, with a plateau tending at higher vWF levels. Using these standard methodologies, and standard plasma dilutions, high-vWF level test samples will tend to fall on or near the plateau, and results will be unreliable, with a tendency to be exaggerated the higher the vWF. These findings have particular relevance to research studies measuring vWF in patients suffering various clinical conditions (e.g., thrombotic thrombocytopenic purpura, diabetes, renal failure) where higher than normal levels of vWF may be anticipated. In these cases, laboratoryderived vWF levels could be "misrepresented" if the study design did not take into account the need to revise the vWF testing procedure.

The laboratory assessment of von Willebrand factor (VWF) is typically performed at specialist laboratory sites, particularly when performed as a battery of laboratory tests in a thorough workup for the diagnosis of von Willebrand's disease (VWD). In these cases, specimens could derive from a variety of off-site sources, including smaller laboratories, and general clinical practitioners. Because of the potential for lack of control by the specialist laboratory over the method of specimen handling and transport from these sources, and recent VWF methodological advances, we investigated the effect of prolonged ambient temperature specimen storage on laboratory assay results. Thus, specimens were collected from 10 separate individuals, and each variably processed to provide an ideal ('control') plasma specimen, and additional specimens that were then stored at ambient temperature for up to 7 days. Specifically, specimens were stored either as whole blood, or as separated plasma, and VWF tested in isolated plasma, post 24 h, post 48 h and post 7 days storage. Three separate laboratory assays for VWF were performed; (i) a standard 'antigen' (antisera-ELISA-based) assay (VWF:Ag), (ii) a standard ristocetin-dependent-platelet-agglutination procedure (VWF:RCof) and (iii) a more recently described ELISA-based functional collagen-VWF binding assay (VWF:CBA). Results can be summarized as follows, (i) Plasma storage: there was no (statistically significant) change in VWF:Ag or VWF:RCof assay results over the 7-day storage period; however, there was a small but statistically significant fall (P= 0.009) in VWF:CBA assay results after 7 days storage of plasma. (ii) Whole blood storage: there was no (statistically significant) change in VWF:Ag, VWF:CBA or VWF:RCof assay results over the 7-day storage period, although the data suggested a trend towards increasing VWF:Ag over time. As a result of the change in assayed VWF:CBA following prolonged plasma storage, a similar small but statistically significant (P= 0.009) change (increase) in the VWF:Ag to VWF:CBA ratio was observed. This ratio has previously been determined to be useful in the differential diagnosis of VWD subtypes, with high VWF:Ag to VWF:CBA ratios potentially indicative of Type 2 VWD. Fortunately, the absolute magnitude of the altered ratio following prolonged plasma storage is unlikely in practice to affect the diagnosis of VWD in most testing cases. Nevertheless, there will be occasional borderline normal cases in whom the change in VWF:CBA, or in the calculated VWF:Ag to VWF:CBA ratio, may otherwise influence a clinical diagnosis of VWD. Caution is therefore suggested in the interpretation of laboratory-derived VWF data, particularly if the specimen is derived as an off-site referral.

No abstract

Caffeine, when administered in moderate (30 mg/kg X d) or high (60 mg/kg X d) doses during pregnancy, was shown to cause significant fetal growth retardation of both sexes. Mortality rate at or soon after birth was significantly higher and litter size significantly lower in the litters treated with 60 mg. The subsequent growth rates were also affected. The experimental pups grew more slowly, with growth plateauing at the same age resulting in smaller adults. The male offspring when subjected to short-term stress (one session) in adulthood showed an intact emergency response, demonstrating an adequate ability to react to a sudden environmental change. A significant decrease in 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity, and consequent reduction in testosterone biosynthesis, in the fetal testes at d 18 and 20 of gestation was also found for both doses of caffeine. Low 3 beta-HSD activity persisted to adulthood in the group receiving 60 mg. Lingering effects were observed in a second litter bred 8 wk after the discontinuation of caffeine consumption. In this second breeding, the offspring of both sexes from both caffeine doses were born significantly smaller when compared to the controls. Persistent effects of caffeine were also found in second-generation rats bred from females who were exposed to caffeine in utero. The pups of both sexes were born significantly heavier after a significantly longer gestation. The subsequent growth did not differ from that of the controls. It was suggested that a changed genetic program in the ovarian germ cells of the first generation and/or a changed uterine environment in the second generation may be implicated.