The treatment effect of rivaroxaban on clot characteristics in patients who present acutely with first time deep vein thrombosis.

BACKGROUND: The acute vascular disease deep vein thrombosis (DVT) requires oral anticoagulants to prevent progression. Monitoring therapeutic efficacy of direct oral anticoagulants (DOAC), including rivaroxaban, is problematic as no reliable test is available. Advances in rheometry have led to the development of a functional coagulation biomarker using Gel Point (GP) analysis which assesses clot structure formation. The biomarker measures incipient clot formation time (TGP) and quantifies fibrin clot structure in terms of fractal dimension (df). OBJECTIVE: This study aimed to investigate clot structure formation in first time DVT and the effect of rivaroxaban treatment. METHODS: This prospective observational cohort study measured the GP and standard laboratory markers at three sample points: pre-treatment and at 20 and 60 days following 15 mg BD and 20 mg OD rivaroxaban respectively. RESULTS: Forty DVT patients (mean age 64 years [SD±14.8]; 23 males, 17 female) were recruited. The results show that DVT vs non-DVT patients did not have a significantly different GP profile (df: 1.72±0.06 vs 1.70±0.06 and TGP: 267±68 sec vs 262±73 sec) with both within the defined healthy index. In addition, rivaroxaban therapy increased TGP to 392 s (±135 s) after 20 days, and subsequently increased to 395 s (±194 s) at 60 days but did not significantly increase df (from 1.69±0.05 to 1.71±0.06). CONCLUSIONS: The results indicate in this cohort of DVT patients there was no underlying hypercoagulable effect as determined by gel point analysis. Furthermore, the anticoagulant effect of rivaroxaban prolonged clotting, suggesting a protective effect against clot formation, without significantly reducing clot microstructural properties.

Application of ROTEM to assess hypercoagulability in patients with lung cancer.

BACKGROUND: Venous thromboembolism (VTE) is common in patients with cancer, contributing significantly to morbidity and mortality Currently, no test reliably identifies patients at increased risk of developing VTE who would therefore benefit from prophylactic intervention. The aim of the current study was to evaluate rotational thromboelastometry (ROTEM) in identifying VTE risk in patients with lung cancer. We also compared parameters of ROTEM in patients with limited and extensive disease. METHODS: Parameters of ROTEM were measured in 67 patients with lung cancer and 72 age-matched healthy controls and compared with conventional markers of haemostasis. Patients were followed up for 12 months and VTE incidence recorded. RESULTS: Lung cancer patients had a reduced clotting time (CT), increased maximum clot firmness (MCF) and increased alpha angle compared with controls. Patients also had significantly higher levels of fibrinogen and PAI-1 than controls and in the former group there was a strong correlation between fibrinogen and both MCF and alpha angle. Six patients developed a VTE during the follow-up period and all had values for MCF at or above the upper limit of normal for EXTEM. CONCLUSIONS: This study demonstrates that several ROTEM parameters are significantly different in lung cancer patients compared to healthy age-matched controls, whereas only one of the parameters measured is significantly different between extensive compared to limited disease. No differences were observed between patients who developed a VTE compared to those who did not, highlighting the limitations of ROTEM use in patients with lung cancer.

Greater collaboration across the disciplines: challenges and opportunities.

This paper reports a panel discussion--Opportunities for and Limitations to Greater Collaboration Across the Disciplines--held at the conference. It highlights the need for greater collaboration between demographers and epidemiologists and notes the institutional and disciplinary challenges to and opportunities for promoting greater cooperation.

A new insertion sequence, ISCb1, from Clostridium beijernickii NCIMB 8052.

The NCIMB 8052 strain of Clostridium beijerinckii contains nine copies of a novel insertion sequence, ISCb1, belonging to the IS4 family. The 1764 bp element has 18 bp inverted repeats at its extremities, and generates 11 bp target repeats upon insertion. It contains a 1365 bp ORF whose predicted product (455 amino acids) resembles bacterial transposases. The highly conserved DD(35)E motif is present, as are signatures characteristic of the N3 and C1 domains of bacterial transposases. Codon usage of the ORF is somewhat different from that of other C. beijerinckii genes, suggesting that ISCb1 may have been acquired from another organism by horizontal gene transfer in the evolutionary past. One ISCb1 copy lies close to the site of insertion of Tn 1545 in a mutant strain, C10, which shows a reduced tendency to degenerate (i.e. loss of the potential to form solvents) compared with the wild type. In the C10 strain, the characteristic pattern of DNA fragments detected by an IS-specific probe was altered, but this was due to the Tn1545 insertion itself, rather than an ISCb1-mediated genome re-arrangement. There is currently no evidence that the element is involved in strain degeneration, since 12 independently isolated spontaneous mutants that had lost the ability to form solvents had the same ISCb1 profile as that of the wild type strain. The element is apparently restricted to a series of closely related solvent-forming clostridia.

Truncation of peptide deformylase reduces the growth rate and stabilizes solvent production in Clostridium beijerinckii NCIMB 8052.

The wild-type strain of Clostridium beijerinckii NCIMB 8052 tends to degenerate (i.e., lose the ability to form solvents) after prolonged periods of laboratory culture. Several Tn1545 mutants of this organism showing enhanced long-term stability of solvent production were isolated. Four of them harbor identical insertions within the fms (def) gene, which encodes peptide deformylase (PDF). The C. beijerinckii fms gene product contains four diagnostic residues involved in the Zn2+ coordination and catalysis found in all PDFs, but it is unusually small, because it lacks the dispensable disordered C-terminal domain. Unlike previously characterized PDFs from Escherichia coli and Thermus thermophilus, the C. beijerinckii PDF can apparently tolerate N-terminal truncation. The Tn1545 insertion in the mutants is at a site corresponding to residue 15 of the predicted gene product. This probably removes 23 N-terminal residues from PDF, leaving a 116-residue protein. The mutant PDF retains at least partial function, and it complements an fms(Ts) strain of E. coli. Northern hybridizations indicate that the mutant gene is actively transcribed in C. beijerinckii. This can only occur from a previously unsuspected, outwardly directed promoter located close to the right end of Tn1545. The Tn1545 insertion in fms causes a reduction in the growth rate of C. beijerinckii, and, associated with this, the bacteria display an enhanced stability of solvent production. The latter phenotype can be mimicked in the wild type by reducing the growth rate. Therefore, the observed amelioration of degeneration in the mutants is probably due to their reduced growth rates.

Accuracy of low electronic platelet counts using platelet distribution curves.

At low platelet levels electronic counts are inaccurate because background counts are an increasingly important contribution to the total count. In this study the background contribution was selectively eliminated by coupling a multichannel particle size analyzer (Coulter Channelyzer II) to an electronic counter (Coulter ZBI). Platelet counts below 50 x 10(9)/l required an adjustment of the lower threshold in 11 of 15 specimens. Non-platelet counts averaged 18 percent of the platelet particle count with a maximum value of 50 percent. In contrast, platelet counts between 50 to 100 x 10(9)/l required only a minimum adjustment of the lower threshold and extraneous counts averaged only 2.7 percent of the platelet particle count. Phase platelet counts ranging from 4.0 x 10(9)/l to 115 x 10(9)/l were compared in ZBI-Channelyzer counts in 30 patients. The electronic counts showed good agreement with the reference method. Results were statistically analyzed using linear regression analysis and paired t tests. Technical errors involved in electronic and visual platelet counts are discussed.

Serum-induced chromosome damage and neoplastic transformation of mouse cells in vitro.

In previous studies, mouse cells grown in medium supplemented with horse serum (HS) developed more chromosomal aberrations and underwent malignant transformation earlier than cells from the same pool grown with fetal bovine serum (FBS) supplement. In the present study cells derived from C3Hf/HeN mouse embryos were grown in medium NCTC-135 supplemented with various combinations of large- and small-molecule fractions of HS and FBS in an effort to determine the effective components. The results indicate that the large-molecule fraction of HS (mare or stallion) produces alterations in chromosome number and structure. HS is also shown to cause chromatid breaks and exchanges at or near the centromere in contrast to fluorescent-light-induced breaks and exchange at or near the centromere in contrast to fluorescent-light-induced breaks which occur randomly along the chromatid. However, efforts to control completely chromosome stability and malignant transformation through the use of large- and small-molecule fractions of HS and FBS or combinations thereof were unsuccessful. In connection with this study, diagnosis of malignant transformation in vitro was made by a direct sampling method based on cytologic criteria previously described and documented. With one exception, the diagnoses of 11 different cell lines were consistent with results of in vivo assays.