The physical spacing between the von Willebrand factor D'D3 and A1 domains regulates platelet adhesion in vitro and in vivo.

Essentials The role of von Willebrand factor (VWF) domains in regulating platelet adhesion was studied in vivo. Multimeric VWF with spacers at the N- and C-terminus of VWF-A1 were systematically tested. N-terminal modified VWF avidly bound platelet GpIbα, causing VWD Type2B like phenotype in mice. Novel anti-D'D3 mAbs suggest that changes at the D'D3-A1 interface may be biologically relevant. SUMMARY: Background Previous ex vivo studies using truncated VWF (von Willebrand factor) suggest that domain-level molecular architecture may control platelet-GpIbα binding function. Objective We determined if this is the case with multimeric VWF in vivo. Methods Full-length human VWF ('hV') was modified with a 22-amino acid mucinous stretch at either the N-terminus of VWF-A1 to create 'hNV' or C-terminus to yield 'hCV'. This extends the physical distance between VWF-A1 and the adjacent domains by ~6 nm. Similar mucin inserts were also introduced into a human-murine chimera ('h[mA1]V') where murine-A1 replaced human-A1 in hV. This yielded 'h[mA1]NV' and 'h[mA1]CV', with N- and C-terminal inserts. The constructs were tested ex vivo and in vivo. Results Mucin insertion at the N-terminus, but not C-terminus, in both types of constructs resulted in >50-fold increase in binding to immobilized GpIbα. N-terminal insertion also resulted in greater shear-induced platelet activation, more thrombus formation on collagen, enhanced platelet accumulation and slower platelet translocation on immobilized VWF in microfluidics assays. Hydrodynamic injection-based expression of h[mA1]NV, but not h[mA1]V or h[mA1]CV, in VWF-/- mice caused profound thrombocytopenia, reduced plasma VWF concentrations, lower multimer distribution, and incessant tail bleeding that is reminiscent of von Willebrand disease type 2B. Platelet plugs were noted in the portal veins and hepatic arteries. An anti-D'D3 mAb DD3.3 that displays enhanced binding to VWF containing the N-terminal mucin insert also exhibited increased binding to wild-type VWF under shear and upon ristocetin addition. Conclusion Conformation changes at the VWF D'D3-A1 interface may be a key regulator of thrombosis in vivo. Structural features at the A1-A2 interface are likely of less significance.

Epidemiology of leprosy in tribals of Adhaura plateau.

A door to door survey was carried out in the Adhaura plateau of Bihar, to find out the magnitude of leprosy problems in that area. Out of a total of 7,521 persons, mostly tribals, 5,476 were examined giving a coverage of 72.8%. Prevalence rate of leprosy was 20.6%/1000 population. Maximum prevalence was seen in the age group of 55 and above. The disease was more common in males and in the literate and educated group. The ratio of tuberculoid was 57.5%, borderline 29.0% and lepromatous 10.0%, indeterminate type constituted 3.5%. The population had a poor nutritional status with caloric intake of 1471 cal per day.

Intraocular pressure changes following modified e.C.T.

Intraocular pressure changes following modified ECT with and without succinylcholine were studied in Sixty cases. The pressure rose in both the conditions though the rise was more marked and longer lasting when succinylcholine was used.