Fluorescence resonance energy transfer between points on tropomyosin and actin in skeletal muscle thin filaments: does tropomyosin move?

BACKGROUND: In patients with ovarian carcinoma, an hematocrit-independent hyperviscosity syndrome is often present. The syndrome is characterized by normal or low hematocrit and hemoglobin concentration, an elevated platelet count, and an increase in clotting factor turnover. Because deep vein thrombosis (DVT) often complicates the course of ovarian carcinoma, the aim of this study was to investigate the possible association of hyperviscosity syndrome with the development of DVT. METHODS: Rheologic estimations of the blood included red blood cell (RBC) aggregation (stasis and low shear), plasma viscosity (pv), blood cell count, and fibrinogen, which were performed before primary surgery and the beginning of perioperative heparin thrombosis prophylaxis on 63 of 65 patients with Stage I-IV ovarian malignancy (according to the staging criteria of the International Federation of Gynecology and Obstetrics). Two patients who had had DVT 5-6 weeks in advance of the study were excluded from rheologic calculations. Thrombosis screening by impedance plethysmography was performed the day before primary major surgery; postoperatively on Days 1, 3, 5, 7, and 10; before each of 6 cycles of chemotherapy (once every 3 weeks); and thereafter once every 3 months during follow-up. All blood tests were also performed on 72 healthy women and 29 patients with benign ovarian tumor the day prior to surgery. RESULTS: All ovarian carcinoma patients, including 7 patients with tumors of low malignant potential, were eligible for surgery, and all except those with Stage IV disease (n = 12) were macroscopically tumor free after surgery. Before surgery, RBC aggregation, pv, and platelet and fibrinogen concentrations were significantly higher (P < 0.05) in cancer patients than in either of the control groups, whereas hemoglobin (hb) and hematocrit (hct) were significantly lower in cancer patients than in healthy women (P < 0.001). Platelet, leukocyte, and fibrinogen concentrations were significantly correlated to disease stage, whereas pv, RBC aggregation, hb, and hct were not. The preoperative pv was significantly higher in patients who later developed DVT (n = 17; 1.46+/-0.13 mPas; P = 0.01) than in those who did not (1.34+/-0.14 mPas). Of all estimated preoperative variables, only pv was a significant risk factor for postoperative and subsequent DVT (RR: 29.84; 95% CI: 1.076-827.16; P = 0.04). CONCLUSIONS: Our results confirm the presence of a hematocrit- and stage-independent hyperviscosity syndrome in untreated ovarian carcinoma patients. In addition, a high preoperative plasma viscosity was a significant risk factor for the development of DVT in the postoperative period and even thereafter.