Leishmania donovani-infected splenic macrophages and P388D1 (P388D1(I)) failed to activate T cells in response to low dose of exogenous peptide. The membrane fluidity of P388D1(I) was greater than that of the normal counterpart P388D1(N), but could be reduced either by exposing the cell below phase transition point or by loading cholesterol into membrane (L-P388D1(I)), and this was associated with enhanced Ag-presenting ability of P388D1(I). Presentation of endogenous leishmanial Ag, kinetoplastid membrane protein-11, was also defective, but could be corrected by loading cholesterol into membrane. Because membrane rafts are important for Ag presentation at a low peptide dose, raft architecture of P388D1(I) was studied using raft (CD48 and cholera toxin-B) and non-raft (CD71) markers in terms of their colocalization with I-Ad. Binding of anti-CD48 mAb and cholera toxin B subunit decreased significantly in P388D1(I), and consequently, colocalization with I-Ad was not seen, but this could be restored in L-P388D1(I). Conversely, colocalization between I-Ad and CD71 remained unaffected regardless of the presence or the absence of intracellular parasites. P388D1(N) and L-P388D1(I), but not P388D1(I), formed peptide-dependent synapse with T cells quite efficiently and this was found to be corroborated with both intracellular Ca2+ mobilization in T cells and IL-2 production. This indicated that intracellular parasites disrupt the membrane rafts, possibly by increasing the membrane fluidity, which could be corrected by making the membrane rigid. This may be a strategy that intracellular L. donovani adopts to evade host immune system.

Vibrio cholerae hemolysin is an extracellular pore-forming monomeric protein with a native molecular weight of about 60,000. In this study, we showed that the hemolysin interacted with immobilized phospholipids and cholesterol and formed oligomers in vesicles constituted from phospholipids alone with a stoichiometry identical to those produced in rabbit erythrocyte membrane. However, the hemolysin bound to glycoproteins with terminal beta1-galactosyl residues and an association constant of 9.4 x 10(7) M(-1) was estimated for the hemolysin-asialofetuin complex by solid phase binding assay. Oligomerization of the hemolysin in lipid bilayer converted the sugar-binding monomer to a lectin with strong carbohydrate-dependent hemagglutinating activity accompanied by inactivation of hemolytic activity and loss in ability to interact with phospholipids. There was no evidence for erythrocyte surface carbohydrates playing an essential role in interaction of the hemolysin with the cell. However, specific glycoproteins inhibited hemolysis of rabbit erythrocytes as well as interaction of the hemolysin with phospholipid. The results suggest (i) V. cholerae hemolysin is a monomer with distinct domains associated with specific binding to carbohydrates and interaction with lipids, (ii) the pore-forming property depends solely on the protein-lipid interaction with no evidence for involvement of sugars, and (iii) specific sugars can down-regulate the ability of the hemolysin to form pores in lipid bilayers.

No abstract

Vibrio cholerae is a gram-negative bacterium that can cause a severe, acute secretory diarrhea. Serological differentiation of V. cholerae strains is based on the O-side chain of the lipopolysaccharide (LPS) component of the outer membrane. Of the more than 200 serogroups of V. cholerae identified, only the O1 and O139 serogroups can cause epidemic cholera (44). These pathogens are noninvasive and colonize the mucosal surface of the small intestine (44).Natural infection with V.

When bodies are brought for autopsy it is sometimes unclear whether the injuries are due to a fall from a height or due to blunt trauma from other causes, especially when the bodies are found near buildings with no eyewitnesses available. Studies discussing the injury patterns in adults after falls exclusively from buildings are rare. A five-year retrospective study was carried out on 151 cases of fatal falls from buildings brought for autopsy. The aim was to assess the pattern of these injuries and identify features helpful in discriminating between these and injuries due to blunt trauma from other causes. The majority of cases comprised subjects who fell from heights of 10-20 feet (3-6m) with most falls occurring late at night or in the early morning. The pattern that emerged is quite distinct from ground level falls and pedestrian injuries. Abrasions are the commonest injury and bruises very rare. Lacerations are mostly on the head and skull fractures are evenly distributed between the vertex, base and vertex plus base. Subarachnoid haemorrhage is the commonest intracranial lesion. Extradural haemorrhage alone is rare. Fractures of ribs and cervical vertebrae are common and fractures of thoracic vertebrae and long bones are uncommon. Safety measures to prevent such falls have been suggested.