Key role of integrin αIIbβ3 signaling to Syk kinase in tissue factor-induced thrombin generation

The fibrin(ogen) receptor, integrin α(IIb)β(3), has a well-established role in platelet spreading, aggregation and clot retraction. How α(IIb)β(3) contributes to platelet-dependent coagulation is less well resolved. Here, we demonstrate that the potent suppressing effect of clinically used α(IIb)β(3) blockers on tissue factor-induced thrombin generation is linked to diminished platelet Ca(2+) responses and phosphatidylserine (PS) exposure. The same blockers suppress these responses in platelets stimulated with collagen and thrombin receptor agonists, whereas added fibrinogen potentiates these responses. In platelets spreading on fibrinogen, outside-in α(IIb)β(3) signaling similarly enhances thrombin-induced Ca(2+) rises and PS exposure. These responses are reduced in α(IIb)β(3)-deficient platelets from patients with Glanzmann's thrombasthenia. Furthermore, the contribution of α(IIb)β(3) to tissue factor-induced platelet Ca(2+) rises, PS exposure and thrombin generation in plasma are fully dependent on Syk kinase activity. Tyrosine phosphorylation analysis confirms a key role of Syk activation, which is largely but not exclusively dependent on α(IIb)β(3) activation. It is concluded that the majority of tissue factor-induced procoagulant activity of platelets relies on Syk activation and ensuing Ca(2+) signal generation, and furthermore that a considerable part of Syk activation relies on α(IIb)β(3) signaling. These results hence point to a novel role of Syk in integrin-dependent thrombin generation.     

Lead metabolism in lactation

Summary A 2-fold increase in lead absorption was observed in lactating animals which received 2 mg Pb/1 in drinking water. About one-half of the absorbed lead was transferred to the litters.Acknowledgments. This work was partially supported by a research grant from the US Environmental Protection Agency and the US Public Health Service.     

Galactose induced Balbiani-ring-like structures in chromosomes I and II ofChironomus thummi

Summary In one strain ofChironomus thummi, galactose feeding of the larvae induced the appearance of 2 Balbiani-ring-like structures on salivary gland chromosomes I and II. This phenomenon may be related to the galactose induction of BR6 inC. pallidivittatus.     

Structure specificity of some immunoadjuvant synthetic glycopeptides

Summary The immunoadjuvant activity of muramyl dipeptide seems to be critically dependent on the type of substitution of the -carboxyl group of the D-isoglutamine residue. Moreover the nonapeptide L-Ala-D-isoGlu-L-Lys-D-Ala-(Gly)₅-OME also shows a definite effect.     

Lymphostatic Retinal Haemangiopathy

Zusammenfassung Verschluss der zervikalen Lymphbahnen führt zu einer lymphostatischen, retinalen Hämangiopathie mit Verdickung und Strukturveränderung der Basalmembranen.     

Occurrence of a characteristic nucleolar structure in pachytene cells

Resumen Se describe el hallazgo de una estructura nucleolar característica en células paquiténicas de anteras deAllium cepa, fijadas en formol y teñidas con fuchsina. Esta estructura se presenta como una pequeña formación semejante a un botón o anillo en el nucleolo de todos los meiocitos observados en ese estadío.

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The work reported in this paper was undertaken during thetenure of a Research Training Fellowship awarded by the International Agency for Research on Cancer.