Reciprocal behaviour associated with altered homeostasis and photosensitivity of Drosophila clock mutants.

The circadian oscillators of genetically short-period and long-period Drosophila exhibit reciprocal behaviour in four distinct ways: (1) with respect to the dependence of period on temperature, (2) in the change of period during constant darkness after ten days of constant light, (3) in the change of period during the second ten days of darkness as compared with the period during the first ten days, and (4) in the period change resulting from exposure to low-intensity constant light. The homeostatic control of the dependence of period length on temperature is impaired in the mutants as compared with wild-type files. The normal Drosophila pacemaker may comprise two mutually coupled oscillators, whereas the mutants may represent a reduction in activity of one or the other constituent oscillator.

Urine and plasma levels of fibrinopeptide B in patients with deep vein thrombosis and pulmonary embolism.

BACKGROUND: Many patients with pulmonary thromboembolism remain undiagnosed, possibly because of the difficulty clinicians have in determining which patients merit work-up with accurate (but expensive) imaging techniques. OBJECTIVES: We present the first prospective clinical study of pulmonary embolism (PE) and deep venous thrombosis (DVT) detection using the FPBtot assay, which measures fibrinopeptide B and its first derivative, des-arginine fibrinopeptide B. METHODS: Twenty three patients with signs or symptoms of PE or DVT were enrolled in the study prior to the performance of definitive testing. Using a novel immunoassay, FPBtot levels were measured in urine and plasma samples from patients as well as from healthy controls. Urine and plasma FPBtot levels were compared to the diagnostic results, as blindly adjudicated by one of the investigators. Patients were excluded if they withdrew (n =1), had inconclusive diagnostic testing (n = 7), or did not give samples (n = 2 for urine, n = 3 for plasma). RESULTS: The mean FPBtot concentration in the urine of the 'DVT/PE positive' group was 78.4 +/- 35.2 ng/ml and 2.7 +/- 1.9 ng/ml in the 'DVT/PE negative' group (p = 0.03). The urine FPB(tot) concentrations in the 'DVT/PE negative' group were not significantly different from those in the healthy control group (2.2 +/- 0.4 ng/ml, p = 0.40). The area under the ROC curve for urine FPB(tot) concentrations was 97.3 +/- 3.8%, suggesting a high degree of diagnostic accuracy. Plasma FPB(tot) concentrations were not significantly different between groups. CONCLUSIONS: Urine FPBtot levels may help detect patients with PE and DVT.

Improved imaging of deep venous thrombi during anticoagulation using radiolabelled anti-D-dimer antibodies.

OBJECTIVES: Radiolabelled anti-fibrin antibodies have not yet enabled reliable and practical diagnosis of venous thromboembolism. However, previous unsuccessful clinical trials were performed with anti-fibrin beta-chain antibodies that do not optimally bind to thrombi during anticoagulation. The current experiments were performed to determine if radiolabelled anti-D-dimer antibodies more reliably allowed nuclear medicine imaging of deep venous thrombi during anticoagulation than anti-beta-chain antibodies. METHODS: Dogs with pre-existing unilateral femoral vein thrombi were anticoagulated with heparin (300 units.kg (-1) bolus followed by 90 units.kg(-1).h(-1) continuous infusion). They were then allocated to receive one of three (111)In labelled antibodies: anti-D-dimer, anti-beta or a non-specific control antibody. Gamma scans of the legs were performed at regular intervals for 24 h. Scans were interpreted in a blinded fashion and the number of gamma counts from the femoral area on the thrombosed side was compared to the contralateral side. Clot/blood isotope density ratios were determined post-mortem. RESULTS: Leg thrombi were 100% detectable in the anti-D-dimer group, but only 60% detectable in the anti-beta group. Mean +/- SD relative counts in the thrombosed femoral area was 137 +/- 10% compared to the contralateral side in the anti-D-dimer group, but only 116 +/- 20% in the anti-beta group. The clot/blood ratio was 24.5 +/- 2.8 in the anti-D-dimer group, but only 7.8 +/- 2.0 in the anti-beta group. CONCLUSIONS: In labelled anti-D-dimer provides superior nuclear medicine images of thrombi during intensive anticoagulation compared to anti-beta. Clinical results with radiolabelled anti-D-dimer may be more promising than those previously observed with other anti-fibrin antibodies.

Embolization itself stimulates thrombus propagation in pulmonary embolism.

The role of active thrombosis in the pathophysiology of pulmonary embolism is unclear. We tested the hypothesis that venous thrombi significantly increase their thrombotic activity once they embolize into the high-flow circulation of the pulmonary arteries. Thrombotic activity was measured using an immunoassay that measures both fibrinopeptide B (FPB) as well as its most abundant metabolite des-arginine FPB. Thrombi were formed in the femoral veins of adult dogs. In one group, the thrombi were embolized without anticoagulation. In the second group, heparin (300 U/kg bolus, then 90 U x kg(-1) x h(-1) infusion) was administered before embolization to prevent subsequent thrombotic activity. Plasma FPB concentrations were significantly suppressed in the heparinized group relative to the nonheparinized group for 1 h postembolization (P = 0.038). We conclude that pulmonary embolization itself causes preexisting venous thrombi to greatly intensify their thrombotic activity and that embolization-associated thrombus propagation can be prevented by heparin.

Single photon emission computed tomography of pulmonary emboli and venous thrombi using anti-D-dimer.

Previous attempts to diagnose thromboemboli using radiolabeled antibodies and nuclear medicine imaging have been disappointing. We present the results of experiments with intravenous technetium-99m-labeled deimmunized antifibrin Fab' fragments to diagnose thromboemboli using single photon emission computed tomography (SPECT), a highly sensitive scintigraphic imaging technique. Pulmonary emboli (PEs) and lower extremity deep vein thrombi (DVTs) were formed in five dogs, then technetium-99m-labeled Fab' ( approximately 400 mg, approximately 260 MBq) were injected via forelimb veins. Thoracic and lower extremity SPECT scans were performed at 2-hour intervals after antibody infusion to visualize the thromboemboli. Four hours after antibody infusion, all PEs and DVTs of mass 0.4 g or greater were clearly visualized on SPECT scans as 'hot spots' within the lungs and legs, respectively. PEs (0.48 +/- 0.09 g) were intensely radiolabeled, yielding clot/blood radioactivity ratios of 22.8 +/- 5.6. DVTs (0.45 +/- 0.31 g) also had high clot/blood ratios (11.7 +/- 2.6). Infusion of these radiolabeled antibody fragments, combined with SPECT, produces clear images of PEs and DVTs within a clinically feasible time frame. The technique reliably identified even peripheral thromboemboli of relatively small size, which are difficult to diagnose with currently available imaging techniques, and may enable imaging of PEs, DVTs, or both in the same patient.