Ganglioside content of human platelets--differences in resting and activated platelets.

Gangliosides may play functional roles in platelet physiology, therefore this study has been designed to evaluate whether changes in ganglioside composition may occur as a consequence of platelet activation. The results obtained indicate that lactosylceramide and GM3 are the major glycosphingolipids of human platelets. The lipid-bound sialic acid (LBSA) content was 1.27 +/- 0.04 micrograms/mg of protein. Resting platelets did not express GD3; GD3 was synthesized upon platelet activation (24 +/- 8 ng/mg of protein). The stimulation of platelets with adenosine diphosphate showed the appearance of GD3 even in the absence of degranulation. Finally, incorporation of pyrene-labeled GM3 into platelet membranes, followed by stimulation with adenosine diphosphate, resulted in the appearance of a fluorescent band comigrating with GD3. The present studies indicate that sialytransferase activation may occur as an early event following platelet stimulation, leading to GD3 synthesis mainly from the GM3 pool.

Determinants of homocysteine levels in colorectal and breast cancer patients.

BACKGROUND: Homocysteinemia has been associated with oncogenic risk. This study was designed to investigate the homocysteine (Hcy) genotype/phenotype interactions together with the inflammatory and nutritional status of cancer patients. PATIENTS AND METHODS: The Hcy levels were analyzed in 47 cancer patients in association with methylenetetrahydrofolate reductase (MTHFR) polymorphisms, folate and inflammatory markers. RESULTS: The MTHFR C677T and A1298C genotype distributions did not differ from those predicted by the Hardy-Weinberg distribution. Conversely, the Hcy levels were higher in the cancer patients (p=0.04), who were also characterized by low-grade inflammation. The Hcy levels correlated with the interleukin-6 (IL-6) (p=0.001), tumor necrosis factor-alpha (TNF-alpha) (p=0.042) and folate (p<0.0001) levels of the patients. Multivariate analysis showed that TNF-alpha (p=0.014) and folate (p=0.019) were independent predictors of elevated Hcy levels in the cancer patients. CONCLUSION: The MTHFR polymorphisms do not significantly contribute to tHcy (total Hcy) levels in cancer patients, and cancer-related inflammation may be associated with elevated tHcy levels, possibly involving a TNF-alpha mediated pathway.

Effects of storage on in vitro platelet responses: comparison of ACD and Na citrate anticoagulated samples.

The present study was designed to evaluate whether the use of acid citrate dextrose (ACD) Formula A may enhance the survival of platelets during storage, thus allowing the continuance of platelet studies over the period of 2-3 hours usually recommended. For this purpose the effects of time on in vitro platelet response to several agonists have been investigated in platelet-rich plasma (PRP) obtained from blood samples anticoagulated with either Na citrate or ACD Formula A. The analysis of the data obtained in in vitro platelet aggregation studies using various parameters and at different time points demonstrated that storage of PRP obtained from citrated samples caused a marked reduction of platelet responses. This reduction was already evident after 6 hours, and a strong decrease was observed after 8 hours with all the agonists used. On the other hand, storage of ACD anticoagulated blood did not cause any significant decrease of platelet responsiveness up to 6 hours. A reduction of platelet aggregation became evident only after 8 hours, but not to the same extent as the one observed in citrated samples. Therefore, it may be concluded that the use of ACD Formula A as anticoagulant is capable of maintaining a normal platelet responsiveness up to 6-8 hours, thus permitting the investigation of platelet function for periods of time over those commonly recommended.

Acid citrate dextrose (ACD) formula A as a new anticoagulant in the measurement of in vitro platelet aggregation.

To evaluate whether the use of ACD Formula A may affect in vitro platelet function, blood samples were obtained from 21 healthy blood donors and anticoagulated in ACD (acid-citrate dextrose, NIH Formula A), Na citrate 3.8%, and K3EDTA. Platelet count, mean platelet volume, and in vitro platelet aggregation were evaluated on each sample. No significant difference was observed in platelet count and mean platelet volume among the different samples. Conversely, the ACD treated platelets showed a higher reactivity to the agonists as demonstrated by a significant increase of the maximum percentages of aggregation induced by ADP, epinephrine, and collagen, as well as a significant decrease of secondary aggregation thresholds to ADP and epinephrine. In conclusion, it may be speculated that ACD Formula A is capable of better maintaining the intraplatelet signal transduction mechanisms during PRP preparation, thus improving the overall responsiveness of platelets.