Physical proximity and functional association of glycoprotein 1balpha and protein-disulfide isomerase on the platelet plasma membrane

Platelet function is influenced by the platelet thiol-disulfide balance. Platelet activation resulted in 440% increase in surface protein thiol groups. Two proteins that presented free thiol(s) on the activated platelet surface were protein-disulfide isomerase (PDI) and glycoprotein 1balpha (GP1balpha). PDI contains two active site dithiols/disulfides. The active sites of 26% of the PDI on resting platelets was in the dithiol form, compared with 81% in the dithiol form on activated platelets. Similarly, GP1balpha presented one or more free thiols on the activated platelet surface but not on resting platelets. Anti-PDI antibodies increased the dissociation constant for binding of vWF to platelets by approximately 50% and PDI and GP1balpha were sufficiently close on the platelet surface to allow fluorescence resonance energy transfer between chromophores attached to PDI and GP1balpha. Incubation of resting platelets with anti-PDI antibodies followed by activation with thrombin enhanced labeling and binding of monoclonal antibodies to the N-terminal region of GP1balpha on the activated platelet surface. These observations indicated that platelet activation triggered reduction of the active site disulfides of PDI and a conformational change in GP1balpha that resulted in exposure of a free thiol(s).     

Mutagenicity of nitrosamines formed from nitrosation of spermidine.

5 nitrosamines formed from the nitrosation of spermidine were investigated for mutagenicity using various strains of Salmonella typhimurium in the presence and absence of S9 mix. Using the plate incorporation method, 3-butenyl-(2-propenyl)-N-nitrosamine, 3-hydroxybutyl (2-hydroxypropyl)-N-nitrosamine, 4-hyroxybutyl-(2-hydroxypropyl)-N-nitrosamine, 4 hydroxybutyl-(3-hydroxypropyl)-N-nitrosamine, and in the liquid test 3-hydroxybutyl-(3-hydroxypropyl)-N-nitrosamine were mutagenic in the absence of S9 mix.     

ATTEMPTED HYBRIDIZATION BETWEEN MONOECIOUS AND DIOECIOUS CLONES OF CHARA

The suggestion has been made that within the genus Chara the condition of monoecism or dioecism is of limited taxonomic significance, and that this character reflects only minor genetic variation, rarely sufficient to prevent hybridization between two otherwise similar clones. Objections have been raised to this suggestion. The present investigation was undertaken to determine whether the eggs of dioecious C. rusbyana could be fertilized by sperm from monoecious C sejuncta, monecious C. zeylanica, or dioecious C. kenoyeri; and in turn whether the eggs of C. sejuncta and C. zeylanica could be fertilized by sperm from C. rusbyana. On the basis of 83 crosses involving 28 clones of the four taxa, we conclude that C. rusbyana is genetically isolated from the other three.     

Genetic variability among populations of Fusicladium species from different host trees and geographic locations in the USA

Peach and almond scab caused by Venturia carpophila and pecan scab caused by Fusicladium effusum result in yield loss, downgrading of fruit, defoliation and subsequent decline of an orchard. To understand the levels of genetic diversity and divergence of pathogens from different hosts and locations 51 isolates were genotyped and analyzed using 10 RAPD and 5 UP-PCR markers, including 18 isolates of V. carpophila from peach trees in the southeastern United States, 12 isolates of V. carpophila from almond trees in California, and 21 isolates of F. effusum (a related species) from pecan trees in the southeastern United States. The combined marker results showed a low incidence of polymorphisms among the peach isolates (4.2 % of markers), but a higher incidence of polymorphisms among the almond isolates (42.0 %) and the pecan isolates (61.0 %). The Dice coefficient of similarity ranged from 0.932 to 1.000 for the peach V. carpophila isolates, 0.214 to 0.976 for the almond V. carpophila isolates, and 0.528 to 0.920 for the pecan F. effusum isolates. UPGMA bootstrap values indicated that UP-PCR data were slightly more robust and, based on the combined data, the UPGMA bootstrap analysis (1,000 runs) gave a high node value (100 %) differentiating all the isolates of V. carpophila from F. effusum and a moderate node value differentiating the peach and almond isolates of V. carpophila (68 %). The results suggest some divergence between the V. carpophila populations of almond trees in California and peach tree populations in the southeastern United States, and different levels of genetic diversity within the two populations.