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The metabolic conversion of glucose to energy and reducing power by platelets is examined. Although platelets concurrently metabolize glucose aerobically and anaerobically, the balance between the cytosolic and mitochondrial pathways is affected not only by physiological activation but also by conditions prevailing during in vitro storage. The development of platelet additive solutions and pathogen reduction technologies point to increased glucose metabolism and consequent high levels of lactate production as the effect of platelet damage, rather than the cause. Consequently a different perspective of the data suggests that reduction rather than support of platelet metabolism in vitro would result in a better quality of stored platelets.

We investigated the effect on in vitro platelet function of hirutonin, a modified hirutonin with an RGD-like motif, a pseudo-RGDS peptide and a linear RGDS peptide. Inhibition of expression of surface fibrinogen on ADP-activated platelets with 40 μM of the peptide was as follows: hirutonin 10±3%, modified chimeric peptide 26±5%, pseudo-RGDS 66±11% and linear RGDS 93±13%. Both hirutonin and the chimeric peptide significantly inhibited ADP-induced platelet activation as detected by CD62 expression. Unlike the RGDS and pseudo-RGDS controls, neither the chimeric peptide nor the parent hirutonin inhibited ADP-induced platelet aggregation even at 140 μM. The chimeric hirutonin peptide reduced ATP release from ADP-stimulated platelets by 40±4%. This inhibition was stronger than that caused by hirutonin (23±13%), but less than the RGDS (90±2%) and pseudo RGDS-peptides (59±11%). Primary platelet haemostasis was slightly but not significantly affected by the peptide at 40 and 80 μM. However, shear-induced platelet adhesion to vWF and especially subsequent aggregate formation was interrupted after the addition of the chimeric peptide. Similar results were obtained with hirutonin. This inhibition was not as marked as with the RGDS- and pseudo-RGDS peptides. Both the parent hirutonin and the chimeric peptide caused prolongation of the clinical coagulation assays aPTT and TT. In conclusion, the chimeric hirutonin peptide with introduction of the RGD motif retained its anticoagulant effect but had little formal disintegrin activity. Instead, it appeared to have novel anti-platelet effects that may be of therapeutic use.

Following infection of cattle with bovine herpes virus-1 there is a state of generalized immunosuppression involving various leukocytes including polymorphonuclear (PMN) leukocytes. Since the PMN is considered to be pivotal in recovery from secondary bacterial infections during bovine respiratory disease, investigations were initiated to determine PMN activity in this disease and whether interferon could modulate PMN activity. In this study, the in vivo administration of recombinant interferon alpha-I1 was shown to increase PMN functions as measured by migration/chemotaxis and generation of reactive oxygen species. This augmented activity of PMN appeared to correlate with the reduction of overall clinical disease, that is, number of sick days, lung lesions and weight loss. In the study administration of interferon by the intranasal or intramuscular route were as effective in stimulating PMN function. Based on these studies it was concluded that the reason for improved performance of calves treated with interferon would be due to its immunomodulatory effects on leukocytes. Although interferon did not alter the initial suppression of PMN functions, these functions returned to normal and exceeded normal activities by 7-9 days post-infection, the time when maximal bacterial activity normally is present.

T-2 toxin is taken up by lymphocytes in 10-15 min in a saturable manner. Uptake is dependent on temperature and partially on the availability of energy. Approx. 10(5) molecules of T-2 toxin are bound per cell, having a mean affinity constant, Ka = 1.6 X 10(7) M-1. The toxin is rapidly dissociated from the cell to leave approx. 10-15% of the original loading in 1 h. It is concluded that T-2 toxin uptake and release do not follow conventional mechanisms.

The tricothecene mycotoxin, T-2 toxin interacts differently with mammalian erythrocytes. Pig, man, rabbit, guinea pig, horse, dog, rat, and mouse erythrocytes are all lysed to a varying degree by T-2 toxin. But cow, sheep, goat, buffalo, and deer erythrocytes are all resistant to hemolysis by T-2 toxin. Since erythrocytes from ruminant animals contain little or no phosphatidylcholine, perhaps the presence of phosphatidylcholine in the membrane is required for the hemolytic action of T-2 toxin. Sheep erythrocytes were used to encapsulate T-2 toxin further confirming the resistance of erythrocytes from animals with ruminant physiology to T-2 toxin lysis.

Although T-2 toxin intoxications have been described as radiomimetic, we find that T-2 toxin does not preferentially affect multiplying cells. Among the targets of T-2 toxin toxicity, DNA, RNA and protein synthesis inhibition are analysed. All three types of macromolecular syntheses are affected by a threshold dose of T-2 toxin which corresponds to the interaction of approx. 1·105 T-2 toxin molecules with the same number of T-2 toxin receptors (Gyongyossy-Issa, M.I.C. and Kachatourians, G.G. (1984) Biochim. Biophys. Acta 803, 197–202). Since toxic effects occur faster at higher toxin concentrations than at lower levels, the time-toxic effect relationship may be defined by a constant. Based on these observations, we hypothesize that complete receptor-occupation is the critical first step in the course of T-2 toxin toxicity events.