In vivo platelet activation in atherothrombotic stroke is not determined by polymorphisms of human platelet glycoprotein IIIa or Ib

Platelet membrane glycoprotein polymorphisms are candidate risk factors for thrombosis, but epidemiological data are conflicting. Thus, demonstration of a genotype-dependent alteration in function is desirable to resolve these inconsistencies. We investigated in vivo platelet activation in acute thrombosis and related this to platelet genotype. Frequencies of the 1b and 2b alleles of the HPA 1a/1b and HPA 2a/2b platelet glycoprotein polymorphisms were determined in 150 (52 men/98 women, mean age 58.3 years) patients with atherothrombotic stroke, and the influence of genotype on markers of platelet activation was assessed. Platelet P-selectin (CD62P) expression and fibrinogen binding was measured using whole blood flow cytometry within 24 h of stroke and 3 months later in 77 patients who provided a repeat blood sample. Results were compared with matched controls. Neither the 1b allele [allele frequency 0.11 vs. 0.13, odds ratio (OR) confidence interval (CI) 0.8 (0.5-1.3)] nor the 2b allele [0.09 vs. 0.07, OR (CI) 1.4 (0.8-2.4)] was significantly over-represented in patients. Increased numbers of activated platelets were found following stroke (acute mean P-selectin expression 0.64% vs. control 0.35%, P < 0.001; acute mean fibrinogen binding 1.6% vs. control 0.9%, P < 0.001). Activation persisted in the convalescent phase (P < 0.001 and P = 0.005 vs. controls for P-selectin and fibrinogen respectively). Expression of P-selectin and fibrinogen was not influenced by either the HPA 1a/1b genotype (P > 0.95 for each marker, Scheffe's test) or the 2a/2b genotype (P > 0.95 for each). Although persisting platelet activation is seen in atherothrombotic stroke, it is independent of HPA 1a/1b and 2a/2b genotypes. These data suggest an underlying prothrombotic state, but do not support the polymorphisms studied as risk factors for thrombotic stroke in this population.

THAI-New Air Injection Technology for Heavy Oil Recovery and In Situ Upgrading

Abstract

THAI-"Toe-to-Heel" Air Injection, is a new EOR process, which integrates advanced technology and horizontal well concepts, to achieve a potentially very high recovery of heavy oil. It can also realize very substantial in situ upgrading by thermal cracking, producing upgraded oil to the surface. The process operates in a gravity stabilized manner by restricting drainage to a narrow mobile zone. This causes the flow of mobilized fluids to enter directly into the exposed section of a horizontal production well. The process can be operated on primary production, asnew technology, as a follow-up to existing technologies, or asa co-process where the advantages of high thermal efficiency are equired. This is achieved by concentrating the energy required for oil mobilization, recovery and thermal upgrading in the reservoir. Combined with clean technology design, THAI offerspathway, to future economic success for the heavy oil industry. Three-dimensional, semi-scaled experimental tests on light "Forties Mix" oil (30.7 °CDATA[API), Clair, West of Shetlands medium heavy oil (20.8 °CDATA[API), and heavy Wolf Lake oil (10.95 °CDATA[API) show that a well-controlled, narrow mobile oil zone is created just ahead of the combustion front. The width of this narrow zone depends on the characteristics of the heavy oil at reservoir conditions and the degree to which the very high viscosity of the cold oil seals the horizontal producer well. Well sealing can be augmented by a novel sleeve-back technique, which allows perforated downstream sections of the well to be shut-in. The application of this technique enabled the light oil test to mimic the operation of a heavy oil reservoir using THAI. Very high oil recoveries were achieved in the tests, up to 85﹪ OOIP. During wet in situ combustion (ISC), Wolf Lake oil was upgraded to 20 °CDATA[API, achieving a reduction in the cold oil viscosity from 100,000 mPas to around 50 mPas.

Introduction

Horizontal and multi-lateral wells are being introduced in ever increasing numbers to achieve further gains in reservoir productivity. Two hundred horizontal wells were drilled a decade ago. Now, one company has reported drilling more than 2,100 horizontalwells in North America(1). Advances have also been achieved in the depths drilled, reaching 8,761m(2) and lengths now reaching up to 11 km. Multi-lateral wells, with four or more side-tracks, are not uncommon and offer further optimization gains. Moreover, this technology will accommodate reservoir faults and problems of structural geology as regular design factors so that strategic placement of the well path is achieved. More recently, a new technique to control gas and water production rates by varying the fluid entry points has been successfully tested(3). The most important advantage of horizontal wells is the increase in the reservoir contact area compared to a vertical well. Horizontal wells have created new possibilities for the implementation of advanced IOR methods, especially in thermal recovery.

Plasma homocysteine concentrations in the acute and convalescent periods of atherothrombotic stroke

BACKGROUND AND PURPOSE

Homocysteine is a proposed causal risk factor for atherosclerosis, but this remains controversial. We measured fasting plasma homocysteine concentrations immediately after atherothrombotic stroke and in the convalescent period to investigate this controversy.

METHODS

One hundred six patients (59 men and 47 women, mean age 57.2 [25 to 70] and 56.5 [26 to 69] years, respectively) were recruited within 24 hours of admission, and 82 patients were resampled at least 3 months later. Fasting total plasma homocysteine (tHcy) concentrations were measured by high-performance liquid chromatography.

RESULTS

Median tHcy in the acute phase of stroke was not significantly higher than in matched control subjects (men 9.2 [range 4.4 to 22.8] versus 8.7 [4.9 to 20] micromol/L, P:=0.09, Mann-Whitney U: test; women 8.1 [4.8 to 32.3] versus 7.6 [3.3 to 14.4] micromol/L, P:=0.58). Median plasma concentrations increased significantly in the convalescent period (from 8.5 [4.8 to 19.2] to 10.1 [4.3 to 31.5] micromol/L, P:<0.001, Wilcoxon signed rank test) and were then significantly higher than in control subjects in both men and women (P:=0.03 and 0.05, respectively, Mann-Whitney U: test). This did not appear to be explained by alteration in the known covariates red-cell folate, serum B(12), or creatinine concentrations.

CONCLUSIONS

Homocysteine concentrations are not elevated after recent atherothrombotic stroke but rise in the convalescent period. These data do not support the hypothesis that raised plasma homocysteine concentrations predate atherothrombotic stroke. Instead, they offer an explanation for the discrepancies between prospective and retrospective studies and suggest that elevated tHcy levels may be caused by the disease process itself.

The importance of locally derived reference ranges and standardized calculation of dilute Russell's viper venom time results in screening for lupus anticoagulant

Three commercial dilute Russell's viper venom time (DRVVT) kits were evaluated at four UK centres experienced at performing lupus anticoagulant (LA) tests. Each centre established a normal reference range for the DRVVT ratio calculated against local pooled normal plasma from 20 healthy normal subjects. Plasma from LA-positive patients and LA-negative thrombophilia patients was also tested. DRVVT ratios and the degree of correction were assessed in a variety of ways to reflect not only the UK national Guidelines, but also the manufacturers' recommendations. The reference range data showed a normal distribution in each case, but considerable variation in the mean and SD between the centres and reagents, with the mean +2SD value ranging from 1.06 to 1.19. The use of an arbitrary DRVVT ratio of < 1.1 as the cut-off value for normality, which is applied in many laboratories, is therefore inappropriate. Although no single kit had a clear overall advantage in terms of sensitivity and specificity, the way in which the screen and confirmation data were analysed had a major impact on the interpretation of the results. A data analysis method employing a mean plus two standard deviations (SDs) cut-off for normality, and judgement regarding confirmation of LA based on a percentage correction of DRVVT ratio, was the simplest and most consistent, with overall sensitivity and specificity values of 81% and 94%, respectively, for uncomplicated LA-positive and LA-negative thrombophilia samples. We conclude that the 1991 BSCH Guidelines are in need of revision, each laboratory should establish its own normal reference range for the DRVVT ratio and a common method should be used for calculating the degree of correction with confirmation reagents, so that LA results can be correctly interpreted between laboratories. Standardizing DRVVT interpretation in this way should improve the consistency of LA detection.

Microclustering of TEL-AML1 translocation breakpoints in childhood acute lymphoblastic leukemia

TEL-AML1 fusions are the most common chromosome translocations in childhood leukemia and often, if not always, occur in utero. We previously reported the genomic sequencing of nine TEL-AML1 translocations and showed unique structural features of a breakpoint cluster region in TEL intron 5. We now report data on sequencing and mapping of TEL-AML1 from an additional 11 patients and, using Monte Carlo statistical methods, have analyzed the intronic distribution of the 24 TEL-AML1 fusion junctions sequenced to date. Compared to a null hypothesis of random breakpoint allocation within TEL intron 5 and AML1 introns 1 and 2, significant microclustering was evident on both TEL and AML1. In contrast to previous reports, the two strongest microclusters on TEL were 3' to an unstable repeat region. AML1 demonstrated four highly significant microclusters, two of which were proximal to exons. We note the necessity of sequencing multiple breakpoints before the description of putative microcluster regions. TEL-AML1 breakpoints may be distributed into microclusters because of specific DNA sequence or chromatin features in susceptible cells. We also report on additional features of breakpoints, including a complex t(12;3;21) in one patient and an inverted sequence in another.

Neurofibromatosis associated with a coronary artery aneurysm

A case of a patient with type 1 neurofibromatosis associated with popliteal and coronary artery aneurysms is described in which cross-sectional imaging provided diagnostic information.

Quality of harvested autologous platelets compared with stored donor platelets for use after cardiopulmonary bypass procedures

Platelet dysfunction has a major contribution in bleeding after cardiopulmonary bypass (CPB) and transfusion of platelets is frequently used to secure haemostasis. Allogeneic platelets prepared for transfusion are functionally impaired. Autologous platelets harvested preoperatively require a shorter storage time before transfusion and their use also avoids the risks associated with transfusion of allogeneic blood products. For the first time, we have compared the functional quality of autologous platelets with allogeneic platelets prepared by two methods, immediately before infusion. Platelet activation was assessed by P-selectin expression and fibrinogen binding using flow cytometry. We also monitored the effects of CPB surgery and re-infusion of autologous platelets on platelet function. Autologous platelet-rich plasma (PRP) contained a significantly lower (P < 0.05) percentage of P-selectin-positive and fibrinogen-positive platelets compared with allogeneic platelet preparations, and also contained a significantly higher (P < 0.05) percentage of responsive platelets. Allogeneic platelets prepared by donor apheresis were more activated and less responsive than those produced by centrifugation of whole blood. In patients' blood, the percentage of platelets expressing P-selectin or binding fibrinogen increased significantly after CPB (P < 0.05), while the percentage of platelets responsive to in vitro agonists was decreased (P < 0.05 in autologous transfusion patients), consistent with platelet activation during the procedure. The percentage of activated platelets decreased (statistically not significant) after re-infusion of autologous PRP. P-selectin expression had returned to pre-CPB levels 24 h post-operatively. Autologous platelet preparations display minimal activation, but remain responsive. Conservation of platelet function may contribute to the potential clinical benefits of autologous transfusion in cardiopulmonary bypass.

Recruitment of the nuclear receptor corepressor N-CoR by the TEL moiety of the childhood leukemia-associated TEL-AML1 oncoprotein

The t(12;21)(p13;q22) chromosomal translocation is the most frequent illegitimate gene recombination in a pediatric cancer and occurs in approximately 25% of common acute lymphoblastic leukemia (cALL) cases. This rearrangement results in the in frame fusion of the 5'-region of the ETS-related gene, TEL (ETV6), to almost the entire acute myeloid leukemia 1 (AML1) (also called CBFA2 or PEBP2AB1) locus and expression of the TEL-AML1 chimeric protein. Although AML1 stimulates transcription, TEL-AML1 functions as a repressor of some AML1 target genes. In contrast to the wild type AML1 protein, both TEL and TEL-AML1 interact with N-CoR, a component of the nuclear receptor corepressor complex with histone deacetylase activity. The interaction between TEL and N-CoR requires the central region of TEL, which is retained in TEL-AML1, and TEL lacking this domain is impaired in transcriptional repression. Taken together, our results suggest that TEL-AML1 may contribute to leukemogenesis by recruiting N-CoR to AML1 target genes and thus imposing an altered pattern of their expression.

High prevalence of iliofemoral venous thrombosis with severe groin infection among injecting drug users in North East Scotland: successful use of low molecular weight heparin with antibiotics

Injecting drug use, mainly of heroin, currently represents a major public health issue in the North East of Scotland. The recent tendency of the committed injecting drug user to inject into the groin has created novel problems for the Infection Unit. Data are presented on 20 consecutive patients admitted between 1994 and 1999 with iliofemoral venous thromboses, often complicated by severe soft tissue infections and bacteraemia as a result of heroin injection into the femoral vein. Nine had coexistent groin abscesses, four had severe streptococcal soft tissue infection of the right thigh, groin and lower abdomen, and two had coincidental soft tissue infections of the upper limb. Nine were bacteraemic on admission. All of the patients were chronic injecting drug users with a median injection duration of 6.5 years. The 18 patients tested for hepatitis C virus were all seropositive. None of the 14 patients tested was positive for HIV. Seventeen patients were treated with subcutaneous low molecular weight heparin (tinzaparin), three having received intravenous unfractionated heparin initially. The tinzaparin was self administered and given for a median duration of seven weeks. One patient declined to have any treatment. Three months after presentation eight patients were asymptomatic, seven had a persistently swollen leg, and five were lost to follow up. None developed clinically apparent pulmonary embolism after institution of anticoagulant therapy. The management of iliofemoral venous thrombosis in injection drug users is problematic because of poor venous access, non-compliance with prescribed treatment, ongoing injecting behaviour, and coexistent sepsis. It is unlikely that a randomised trial of standard treatment with heparin and warfarin versus low molecular weight heparin alone would be practical in this patient group. These retrospective data indicate that the use of tinzaparin in injecting drug users is feasible and appears to result in satisfactory clinical responses. The possibility of concomitant infection in injecting drug users with venous thrombosis should always be addressed, as it appears to be a common phenomenon. Early drainage of abscesses and antimicrobial chemotherapy, often administered intramuscularly or orally because of lack of peripheral venous access, is central to the appropriate care of these patients.

Management of urticaria

Urticaria is a very common and disabling disorder. Recent advances in understanding of pathomechanisms has led to important advances in diagnosis and treatment. However, the cause in many patients remains obscure and the treatment poorly effective.

Chronic urticaria: diagnostic recommendations

A group of European recognized dermatologists - the European Working Group on the Diagnosis of Chronic Urticaria - met on 12 March 1999 to discuss best practice for assessing and diagnosing patients with chronic urticaria. These are their recommendations. The recommendations will be valuable for the majority of cases, but are not exhaustive and may not include every possible precipitating factor.

Chronic urticaria

Chronic urticaria remains a major problem in terms of etiology, investigation, and management. It is important to identify patients in whom physical urticaria is the principal cause of disability. Once confirmed by appropriate challenge testing, no further investigation is required. Urticarial vasculitis (UV) is a major differential diagnosis of "idiopathic" urticaria (CIU). I perform biopsy of most patients in this category because UV cannot be considered confirmed in the absence of histologic evidence. Patients with confirmed UV need to be thoroughly investigated for paraproteins, lupus erythematosus hepatitis B and C, and inflammatory bowel disease. Of patients with CIU, a few (<5%) prove to have food additive reactivity confirmed by placebo-controlled challenge testing. There is no convincing evidence of the involvement of Helicobacter pylori or parasite infestation as a cause of chronic urticaria, although H pylori could have an indirect role. Recently it has become clear that 27% to 50% of patients with CIU have functional autoantibodies directed against the alpha-chain of the high-affinity IgE receptor or less commonly against IgG. These antibodies, whose involvement has now been independently confirmed in several centers, are identified by autologous serum skin testing and confirmed by histamine release studies or immunoblotting. Their removal (by intravenous Ig or plasmapheresis) or treatment by cyclosporine has proved highly beneficial in severely affected patients. However, the routine treatment of all CIU patients, irrespective of etiology, remains the judicious use of H(1) antihistamines.

A one-centre prospective audit of peri- and postoperative blood loss and transfusion practice in patients undergoing hip or knee replacement surgery

We prospectively audited peri-operative blood loss and blood transfusion practice in 42 elderly patients (mean age, 71.8 years, 68% female) undergoing hip or knee surgery in an orthopaedic unit. Only in 57% of all operations was blood loss recorded. Compliance with the Maximum Surgical Blood Ordering Schedule (MSBOS) was variable, and Cross-matching to Transfusion (C/T) ratios were low. In 86% of operations, blood had been issued pre-operatively (average three units, range = 1-61 units). Of these patients, 75% subsequently received a transfusion. In 26% of all the operations, the transfusion, although confirmed by the blood transfusion laboratory records, had not been recorded in the medical or nursing notes. The average pre-operative Hb in the transfusion group was 123 g/l (range, 80-144 g/l) and 112 g/l postoperatively and after a transfusion (range, 75-133 g/l). This compared to the non-transfusion group's value of 124 g/l (range, 86-186 g/l) and 113 g/l (range, 77-147 g/l) postoperatively. The high blood issuing and transfusion rates raise the concern that transfusions are being given in response to habit or blood availability, and not medical indications. This would imply that some patients are exposed to unnecessary risks. Furthermore, inadequate documentation of the transfusion process opens the medical profession to criticism and medical, legal and ethical complications regarding patient care. Positive improvements suggested by regular medical audit may help address these problems.

Molecular genetics, natural history and the demise of childhood leukaemia

The patterns of genetic change, clonal evolution, natural history and latency are very different in the paediatric leukaemias compared with adult epithelial cancers but are similar to those in other childhood cancers of mesenchymal stem cell origin. This distinction has a biological logic in the context of the selective pressures for clonal emergence in different developmental and cellular contexts and has a major impact on curability. Most childhood leukaemias and some other mesenchymal stem cell tumours are of fetal origin and can metastasize without corruption of restraints on cell proliferation or bypassing apoptosis. In marked contrast to most invasive or metastatic epithelial carcinomas in adults, these former cancers then retain sensitivity to therapeutic apoptosis. Moreover, their abbreviated and less complex evolutionary status is associated with less genetic diversity and instability, minimising opportunity for clonal selection for resistance. A minority of leukaemias in children and a higher fraction in adults do, however, have genetic alterations that bypass cell cycle controls and apoptosis imposition. These are the 'bad news' genotypes. The cellular and molecular diversity of acute leukaemia impacts also on aetiology. Paediatric acute leukaemias can be initiated prenatally by illegitimate recombination and fusion gene formation in fetal haemopoiesis. For acute lymphoblastic leukaemia (ALL) in children, twin studies suggest that a secondary postnatal molecular event is also required. This may be promoted by an abnormal or delayed response to common infections. Even for a classic case of a cancer that is intrinsically curable by systematic chemotherapy i.e. childhood ALL, prevention may turn out to be the preferred option.

JC and BK virus sequences are not detectable in leukaemic samples from children with common acute lymphoblastic leukaemia

Epidemiological evidence suggests that childhood leukaemia, and possibly common acute lymphoblastic leukaemia in particular, may have an infectious aetiology. Smith (1997 J Immunother 20: 89-100) recently suggested that the critical infectious event occurs during pregnancy, and identified the polyoma virus JC as a candidate agent. In the present study we investigated whether genomes from the JC virus, and closely related BK virus, could be detected in leukaemic cells. No positive results were obtained suggesting that JC virus is unlikely to play a direct role in leukaemogenesis.

Thrombosis, markers of thrombotic risk, indwelling central venous catheters and antithrombotic prophylaxis using low-dose warfarin in subjects with malignant disease

Markers of thrombotic risk--fibrinogen, factor VIII and immunoglobulin G (IgG) anticardiolipin titres--were measured, and the presence of lupus anticoagulant and factor V Leiden were assessed in 84 patients with a solid or haematological malignancy. These patients were monitored, following the insertion of an indwelling venous catheter, for thrombosis. Fifty-five were given prophylactic low-dose warfarin. Over a mean of 15 weeks there were 10 (12%) thrombotic events in 10 patients. Seven were on warfarin. Haemorrhagic problems occurred in three (5%), all on warfarin. Of the 84 patients, 86% had raised fibrinogen levels, 37% elevated factor VIII and 44% raised anticardiolipin levels. Lupus anticoagulant was present in five and three were heterozygous for factor V Leiden. A high prevalence of a range of prothrombotic changes was confirmed and the frequent presence of low-titre anticardiolipin antibody in subjects with malignancy demonstrated. However, none of these parameters predicted the development of thrombosis (P > 0.05).

Structure and possible mechanisms of TEL-AML1 gene fusions in childhood acute lymphoblastic leukemia

TEL-AML1 gene fusion derived by chromosomal translocation is a common acquired genetic lesion in pediatric cancer that is present in approximately 25% of B-cell precursor acute lymphoblastic leukemias, and recent evidence suggests that this recombination event may initiate leukemogenesis prenatally during fetal hemopoiesis. Analysis of the DNA sequence and structure surrounding the breakpoints may reveal clues to their formation. A long-distance inverse PCR strategy was used to amplify TEL-AML1 genomic fusion sequences from diagnostic DNA from nine patients. Breakpoints were scattered within the 14 kb of intronic DNA between exons 5 and 6 of TEL and in two putative cluster regions within AML1 intron 1. Fusion sequences exhibited characteristic signs of nonhomologous end joining, including microhomologies at the end points, and small deletions and duplications. DNA sequences near the breakpoints did not reveal any consistent characteristic signal sequences of the V(D)J recombinase, topoisomerase II consensus sites, or other sequence motifs associated with recombination. However, several translocations occurred near a repeat region of TEL that was found to be highly polymorphic. This region was cloned and found in nuclease sensitivity assays to exhibit paranemic structures, which may have contributed to DNA breakage or illegitimate recombination. The data are compatible with the possibility that TEL-AML1 translocations occur by nonhomologous recombination involving imprecise, constitutive repair processes following DNA double-strand breaks.