Induction of platelet activation by cobra venom factor from Naja naja atra in rat.

AIM: To study the effects of cobra venom factor (CVF) on platelets of rat platelet rich plasma (PRP) and to elucidate its cellular mechanism. METHODS: PRP was used to measure platelet aggregation and ATP-release simultaneously; prothrombinase, intracellular free calcium, and cAMP were assayed using chromogenic substrate, fluorophor Fura-2, and RIA respectively. RESULTS: From 19.5 nmol.L-1 to 617 nmol.L-1 CVF induced platelet aggregation and ATP release concentration-dependently. The ATP release induced by CVF 195 nmol.L-1 was independent of aggregation and was much weaker than that induced by thrombin 1 U/ml. CVF 195 nmol.L-1 increased the prothrombinase activity on platelet surface in a time-dependent manner. SZ-1, SZ-21, and SZ-22, which are monoclonal antibodies against glycoproteins I b/IX, IIIa, and IIb located on platelet membranes, inhibited CVF-induced platelet aggregation. CVF 195 nmol.L-1 also elevated moderately intracellular free calcium ion from (141 +/- 46) to (240 +/- 64) nmol.L-1 in Fura-2 AM loaded platelets, and decreased intracellular cAMP. CONCLUSION: Complement activator CVF induced platelet aggregation and ATP release, and increased prothrombinase activity on platelet surface. These actions were dependent on fibrinogen receptors on the platelet surface, elevation in intracellular free calcium ion, and reduction in cAMP.

Vertical transmission of human immunodeficiency virus type 1: frequency and correlation of transmission (review).

Child bearing age women constitute the fastest growing subset of the human immunodeficiency virus (HIV) infected population. Consistent with this fact is the increasing number of HIV infected children. Vertical transmission from mother to child is the most common route of infection. Because of the nature of the virus, it is difficult to determine the timing of infection. There are three time periods during which infection can occur: prenatally, perinatally, or postnatally. Evidence for each is presented within this review.

Transient population bypassed by polio vaccination programmes in Yunnan Province, China.

PIP: Four wild strains of polioviruses were isolated between 1995 and April 1996 around the Myanmar border with China. This may have occurred because immunization programs missed certain groups of children who migrated with their parents when they were searching for work. Market tradespeople, in particular, travel with their children. Since it is illegal for persons to live where they are not registered and for parents to have more than the number of children permitted by the family planning law, these children may not participate in national immunization days (NIDs) out of fear of being identified. In September and October of 1996, four markets in Yunnan Province were surveyed to determine the proportion of transients and the prevalence of oral polio vaccine (OPV) immunization; parents and guardians of 127 children, who appeared to be under the age of 5 years, were interviewed. The analysis included 91 children (45 boys and 46 girls), aged 1-3 years, who had complete information. Children were grouped as follows: 1) 37 nontransients who lived where their families were registered; 2) 15 transients from within Yunnan Province; 3) 32 transients from other provinces; and 4) 7 foreign transients. The following information was obtained for each child: 1) whether the child had received a routine OPV; 2) whether the child had a BCG scar; 3) whether the child had ever participated in a NID; and 4) whether the child had participated in the 9 supplementary OPV campaigns since 1990. There were no significant differences in sex or age between groups. As shown in a table of survey results, all indices of immunization were lower in transients. Of the nontransient children, 94.6% had received an OPV; 86.5% had a BCG scar; 89.2% had participated in a NID; and 89.2% had received OPV supplementation. The same figures for all transients as a group were 44.4%, 50.0%, 37.0%, and 38.9%, respectively. For the intraprovincial group, the figures were 66.7%, 46.7%, 60.0%, and 46.7%, respectively. For the extraprovincial group, the figures were 34.4%, 53.1%, 21.9%, and 37.5%, respectively. For foreign transients, the figures were 42.9%, 42.9%, 57.1%, and 28.6%, respectively.^ieng