Exercise transiently increases the density of incipient blood clots in antiplatelet-treated lacunar stroke patients

INTRODUCTION

Older individuals and, in particular, individuals at risk of recurrent stroke, may be susceptible to thrombosis when participating in exercise, however, this aspect has not been well investigated.

METHODS

Clot microstructure and conventional markers of thrombotic risk were determined in twenty lacunar stroke patients and fifteen healthy age-matched controls before, immediately after and 1 h after a bout of moderate intensity cycling exercise. Data were analyzed using a linear mixed model approach.

RESULTS

At rest, clot microstructure (1.69 ± 0.07 vs. 1.64 ± 0.05, corresponding to a difference of ~ 50% in normalized clot mass; p = 0.009) and thrombocyte count (73%; p < 0.0001) were higher, and activated partial thromboplastin time was lower (18%; p = 0.0001) in stroke patients compared to age-matched controls. Acute exercise increased thrombogenic markers similarly in the two groups: incipient clot microstructure (1.69 ± 0.07 vs. 1.74 ± 0.05; p = 0.0004 and 1.64 ± 0.05 vs. 1.71 ± 0.04; p < 0.0001, for stroke and controls respectively), plasma fibrinogen (12%; p < 0.0001 and 18%; p < 0.0001, for stroke and controls respectively) and the combined coagulation factors II, VII and X (p = 0.0001 and p < 0.0001, for stroke and controls respectively).

CONCLUSION

The results show that exercise transiently increases the risk of blood clot formation in both stroke patients and controls, however, due to the higher baseline thrombogenicity in stroke patients, the post exercise risk of forming blood clots may be higher in this group.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov (NCT03635177).

Impaired fibrinolysis in severe Covid-19 infection is detectable in early stages of the disease

BACKGROUND

A significant degree of mortality and morbidity in Covid-19 is due to thromboembolic disease. Coagulopathy has been well described in critically unwell patients on ICU. There is less clear evidence regarding these changes at the time of presentation to the Emergency Department and the progression of disease over time.

OBJECTIVE

We sought to investigate whether coagulation markers can predict severity and how they change over the disease course.

METHODS

Patients presenting to a single University Teaching Hospital were recruited and followed up if PCR was positive. Alongside routine blood testing, Rotational Thromboelastometry (ROTEM) was performed. Outcome data was recorded for all patients, and ROTEM values were compared across outcome groups.

RESULTS

Extem and Intem Maximum Lysis were significantly reduced in those who died or required an ICU admission, indicating a reduced ability to break down clot mass in the most critically unwell patients.

CONCLUSION

Comparisons between groups demonstrated that one distinguishing feature between those who require ICU admission or die of Covid-19 compared with those who survive a hospital stay to discharge was the extent to which fibrinolysis could occur. Mortality and morbidity in Covid-19 infection appears in part driven by an inability to break down clot mass.

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.

The effect of the acute inflammatory response of burns and its treatment on clot characteristics and quality: A prospective case controlled study

INTRODUCTION

Burns are known to have an effect on coagulation in the early period after burn. Current coagulation tests have been criticised in acute burns due to their inherent limitations. This study aims to investigate the potential for a new quantitative functional biomarker of clot quality, fractal dimension, to identify changes in clot microstructure as a result of the burn inflammatory response and its treatment.

METHODS

A total of fifty-eight burn patients were included in this prospective case-controlled study. The control group (29 patients mean TBSA 1%), and case group (29 patients mean TBSA 30%) were compared at baseline and the case group investigated further over four time points (baseline, 12h, 24h and 5-7 days). Fractal analysis was performed, as well as current markers of coagulation, inflammatory markers and point-of-care tests, Thromboelastography and Multiplate analysis.

RESULTS

Fractal dimension did not differ between groups at admission (1.73±0.06 and 1.72±0.1), and fell within the healthy index normal range (1.74±0.7), suggesting a normal clot microstructure in the early period after burn. Fractal dimension significantly reduced from baseline over the first 24h following injury (1.59±0.03 p<0.005), indicating a significant reduction in mechanical clot strength and functionality consistent with a hypocoagulable state, not identified with other markers.

CONCLUSIONS

This is the first study to quantify the changes in clot microstructure following burn injury. This study confirms clot microstructure is significantly altered during the first 24h after burn, with the production of a weaker, more porous fibrin clot, consistent with a hypocoagulable state.

Constraints on Minute-Scale Transient Astrophysical Neutrino Sources

High-energy neutrino emission has been predicted for several short-lived astrophysical transients including gamma-ray bursts (GRBs), core-collapse supernovae with choked jets, and neutron star mergers. IceCube's optical and x-ray follow-up program searches for such transient sources by looking for two or more muon neutrino candidates in directional coincidence and arriving within 100 s. The measured rate of neutrino alerts is consistent with the expected rate of chance coincidences of atmospheric background events and no likely electromagnetic counterparts have been identified in Swift follow-up observations. Here, we calculate generic bounds on the neutrino flux of short-lived transient sources. Assuming an E^{-2.5} neutrino spectrum, we find that the neutrino flux of rare sources, like long gamma-ray bursts, is constrained to <5% of the detected astrophysical flux and the energy released in neutrinos (100 GeV to 10 PeV) by a median bright GRB-like source is <10^{52.5}  erg. For a harder E^{-2.13} neutrino spectrum up to 30% of the flux could be produced by GRBs and the allowed median source energy is <10^{52}  erg. A hypothetical population of transient sources has to be more common than 10^{-5}  Mpc^{-3}  yr^{-1} (5×10^{-8}  Mpc^{-3}  yr^{-1} for the E^{-2.13} spectrum) to account for the complete astrophysical neutrino flux.

Swift and NuSTAR observations of GW170817: Detection of a blue kilonova

With the first direct detection of merging black holes in 2015, the era of gravitational wave (GW) astrophysics began. A complete picture of compact object mergers, however, requires the detection of an electromagnetic (EM) counterpart. We report ultraviolet (UV) and x-ray observations by Swift and the Nuclear Spectroscopic Telescope Array of the EM counterpart of the binary neutron star merger GW170817. The bright, rapidly fading UV emission indicates a high mass (≈0.03 solar masses) wind-driven outflow with moderate electron fraction (Y_e ≈ 0.27). Combined with the x-ray limits, we favor an observer viewing angle of ≈30° away from the orbital rotation axis, which avoids both obscuration from the heaviest elements in the orbital plane and a direct view of any ultrarelativistic, highly collimated ejecta (a γ-ray burst afterglow).

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger

Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.

Effects of unidirectional flow shear stresses on the formation, fractal microstructure and rigidity of incipient whole blood clots and fibrin gels

Incipient clot formation in whole blood and fibrin gels was studied by the rheometric techniques of controlled stress parallel superposition (CSPS) and small amplitude oscillatory shear (SAOS). The effects of unidirectional shear stress on incipient clot microstructure, formation kinetics and elasticity are reported in terms of the fractal dimension (d_f) of the fibrin network, the gel network formation time (T_GP) and the shear elastic modulus, respectively. The results of this first haemorheological application of CSPS reveal the marked sensitivity of incipient clot microstructure to physiologically relevant levels of shear stress, these being an order of magnitude lower than have previously been studied by SAOS. CSPS tests revealed that exposure of forming clots to increasing levels of shear stress produces a corresponding elevation in d_f, consistent with the formation of tighter, more compact clot microstructures under unidirectional flow. A corresponding increase in shear elasticity was recorded. The scaling relationship established between shear elasticity and d_f for fibrin clots and whole blood confirms the fibrin network as the dominant microstructural component of the incipient clot in terms of its response to imposed stress. Supplementary studies of fibrin clot formation by rheometry and microscopy revealed the substantial additional network mass required to increase d_f and provide evidence to support the hypothesis that microstructural changes in blood clotted under unidirectional shear may be attributed to flow enhanced thrombin generation and activation. CSPS also identified a threshold value of unidirectional shear stress above which no incipient clot formation could be detected. CSPS was shown to be a valuable haemorheological tool for the study of the effects of physiological and pathological levels of shear on clot properties.

PO-25 - FATCAT: an observational cohort study investigating fractal dimension (df) as a biomarker of thrombogenicity in cancer associated thrombosis during chemotherapy for lung cancer

INTRODUCTION

Venous thromboembolism (VTE), comprising deep vein thrombosis (DVT) and pulmonary embolism (PE) are common complications in patients with cancer, affecting up to 18% of patients. VTE risk is increased by surgery and disease progression, whilst chemotherapy further increases risk up to 7-fold compared to patients without cancer. VTE contributes significantly to morbidity and mortality in patients with cancer, and is the second most common cause of death. Lung cancer is well established to be high risk for VTE, with up to a 22-fold increase in VTE risk associated with this malignancy, and 12% incidence in a recent study of patients with lung cancer undergoing chemotherapy. Furthermore, platinum based chemotherapy agents used in treatment of lung cancer are further associated with increased VTE risk.

AIM

Current risk assessment tools have little value in predicting VTE risk, but prophylactic anticoagulation of patients with cancer increases bleeding incidence and no overall survival benefit. There is therefore a need for a pragmatic test with which assesses coagulation in patients with cancer, and potentially predict VTE risk, leading to personalised management and targeted treatment. We have previously demonstrated that fractal dimension (df) is sensitive to changes in clot microstructure in patients with lung cancer, assessing global coagulation in these patients. Furthermore, df is significantly different in patients with extensive disease (stages 3&4), which conventional laboratory markers failed to identify. Given the increased risk of VTE associated with chemotherapy, FATCAT will aim to assess changes in df in a larger cohort of patients with lung cancer undergoing chemotherapy, quantifying changes in df and relating these to clinical outcome.

MATERIALS AND METHODS

This is a prospective observational cohort study investigating changes in df in patients with lung cancer undergoing chemotherapy. Patients will have a new diagnosis of cytologically or histologically confirmed lung cancer planned for chemotherapy and no history of previous cancer treatment, any thromboembolic / haemostatic disorders or be on anticoagulation.

RESULTS

Following a power calculation, 300 patients will be recruited and followed up for 1 year. df, Doppler ultrasonography and standard coagulation markers will be performed on recruitment, at the mid point, and on completion of chemotherapy in line with standard diagnostic procedures i.e. CT scanning.

CONCLUSIONS

The primary endpoint of the study will be VTE diagnosis, whilst secondary outcomes will determine the change in df during and after treatment with chemotherapy.

The incidence of acute pancreatitis: impact of social deprivation, alcohol consumption, seasonal and demographic factors

BACKGROUND

The incidence of acute pancreatitis has increased sharply in many European countries and the USA in recent years.

AIM

To establish trends in incidence and mortality for acute pancreatitis in Wales, UK, and to assess how incidence may be linked to factors including social deprivation, seasonal effects and alcohol consumption.

METHODS

Use of record linked inpatient, mortality and primary care data for 10,589 hospitalised cases of acute pancreatitis between 1999 and 2010.

RESULTS

The incidence of acute pancreatitis was 30.0 per 100,000 population overall, mortality was 6.4% at 60 days. Incidence increased significantly from 27.6 per 100,000 in 1999 to 36.4 in 2010 (average annual increase = 2.7% per year), there was little trend in mortality (0.2% average annual reduction). The largest increases in incidence were among women aged <35 years (7.9% per year) and men aged 35-44 (5.7%) and 45-54 (5.3%). Incidence was 1.9 times higher among the most deprived quintile of patients compared with the most affluent (3.9 times higher for alcoholic acute pancreatitis and 1.5 for gallstone acute pancreatitis). Acute pancreatitis was increased significantly during the Christmas and New Year weeks by 48% (95% CI = 24-77%) for alcoholic aetiology, but not for gallstone aetiology (9%). Alcoholic admissions were increased with higher consumption of spirits and beer, but not wine.

CONCLUSIONS

The study shows an elevated rate of alcoholic acute pancreatitis during the Christmas and New Year period. Acute pancreatitis continues to rise, most rapidly for young women, while alcoholic acute pancreatitis is linked strongly with social deprivation.

Hospitalized incidence and case fatality for upper gastrointestinal bleeding from 1999 to 2007: a record linkage study

BACKGROUND

Upper gastrointestinal (GI) bleeding is the most common emergency managed by gastroenterologists.

AIM

To establish the hospitalized incidence and case fatality for upper GI bleeding, and to determine how they are associated with factors including day of admission, hospital size, social deprivation and distance from hospital.

METHODS

Systematic record linkage of hospital in-patient and mortality data for 24 421 admissions for upper GI bleeding among 22 299 people in Wales from 1999 to 2007.

RESULTS

The hospitalized incidence of upper GI bleeding was 134 per 100 000. Case fatality was 10.0%. Incidence was stable from 1999 to 2007; case fatality fell from 11.4% in 1999-2000 to 8.6% in 2006-7. Incidence was associated significantly with social deprivation. Compared with weekday admissions, case fatality was 13% higher for weekend admissions and 41% higher for admissions on public holidays. There was little variation in case fatality according to social deprivation, hospital size or distance from hospital.

CONCLUSIONS

Incidence, but not case fatality, was associated significantly with social deprivation. The higher mortality for weekend and public holiday admissions could not be explained by measures of case mix and may indicate a possible impact of reduced staffing levels and delays to endoscopy at weekends in some hospitals.

Detection of clonal immunoglobulin gene rearrangements in the peripheral blood progenitor cells of patients with multiple myeloma: the potential role of purging with CD34 positive selection

Aims-To determine the extent of clonal cell contamination of peripheral blood progenitor cell (PBPC) collections in patients with multiple myeloma (MM) and to assess the purging efficacy of CD34 positive selection.Methods-PBPC collections from 29 patients with MM were analysed for the presence of clonal immunoglobulin heavy chain (IgH) gene rearrangements with a fluorescence based PCR technique. In addition, the PBPC from eight of the 29 patients were "purged" by selection of CD34 positive haematopoietic progenitors with an avidin-biotin immunoabsorption column (Ceprate). In each case the unmanipulated PBPC, CD34 positive and waste fractions were all assessed for the presence of clonal IgH rearrangements.Results-Clonal IgH rearrangements (identical with those demonstrated in diagnostic bone marrow samples) were demonstrated in 10 (35%) of 29 cases and seemed to be confined to those with significant residual bone marrow disease. Clonal rearrangements were evident in the PBPC of two of the eight patients who underwent CD34 selection; in both instances a "clonal purge" was seen as it was not possible to demonstrate the clonal rearrangement in the CD34 positive fraction. In four of the six remaining cases the normal polyclonal fingerprint could not be demonstrated in the CD34 positive fraction, which is consistent with a significant reduction in contaminating B cells.Conclusions-Clonal cells contaminate PBPC collections in a significant proportion of patients with MM and may be eliminated by CD34 positive selection.

Studies of whole blood coagulation by oscillatory shear, thromboelastography and free oscillation rheometry

We report studies of the coagulation of samples of whole human blood by oscillatory shear techniques, including Fourier Transform Mechanical Spectroscopy (FTMS). These techniques are used herein to identify the Gel Point of coagulating blood in terms of the Chambon-Winter Gel Point criterion which provides a rheometrical basis for detecting the establishment of an incipient clot. A comparison of the results of FTMS with those obtained from measurements involving a Thromboelastograph (TEG) and a Free Oscillation Rheometer (FOR) indicate that the latter techniques are not capable of detecting the incipient clot, whose establishment occurs several minutes prior to TEG or FOR-based assessments of clot formation time. The results of the present study suggest that FTMS is a useful tool in blood clotting research, being capable of providing a global coagulation profile in addition to detecting the instant of incipient clot formation.

Rheometry and associated techniques for blood coagulation studies

This review considers various rheometrical approaches that have been adopted to study blood coagulation, with special reference to the rheological assessment of clotting time and studies of the evolution of viscoelasticity during the course of fibrin polymerization and cross-linking. The significance of the Gel Point in blood coagulation studies is discussed as a common feature of many of these studies in that they attempt to detect a liquid-to-solid transition during coagulation. Coagulation studies based on various forms of complex shear modulus measurements are considered, the latter being based principally on controlled stress and controlled strain rheometers. Also considered are the long established technique of thromboelastography and several emerging techniques such as wave propagation measurements, free oscillation rheometry, quartz crystal microbalance measurements and surface plasmon resonance.

Paroxysmal supraventricular tachycardia: improving diagnosis and management within the accident and emergency department

Accident and emergency (A&E) senior house offices (SHOs) have difficulties in interpreting the electrocardiogram (ECG) in narrow complex tachycardia. Correct ECG interpretation is fundamental to patient management in paroxysmal supraventricular tachycardia. This study aimed to assess the ability of A&E SHOs to interpret the ECG in this setting. Correct diagnosis in 63% of cases improved to 86% with the introduction of a standard protocol sheet. Ensuring that SHOs follow agreed guidelines in rhythm recognition and management of PSVT improves patient care.

Prospective double-blind randomized study of the effects of four intravenous fluids on platelet function and hemostasis in elective hip surgery

A prospective randomized double-blind study was performed to determine the effects of three colloids, Haemaccel, Gelofusine and albumin, and also saline on platelet activation, platelet aggregation (induced by adenosine diphosphate (ADP), epinephrine, collagen) platelet agglutination by ristocetin and other hemostatic variables in 55 patients undergoing primary unilateral total hip replacement. The fluids were administered according to normal clinical practice and assessments were made immediately before, at the end, and 2 h after the end of surgery. Surgery was accompanied by thrombin generation (increases in thrombin/antithrombin III complex, prothrombin F1 +2 fragment) platelet activation (betaTG) and compromised coagulation. Generally, the platelet activation appeared to result in platelet desensitization and brought about a persistent reduction in platelet aggregation to ADP and epinephrine, irrespective of the fluid used. Additionally, Haemaccel and Gelofusine inhibited ristocetin-induced platelet agglutination and albumin inhibited collagen-induced platelet aggregation. Gross inhibitory effects of Haemaccel that had been predicted from an earlier in vitro study did not occur. Particular fluids had selective additional effects on the hemostatic system. Albumin infusion served to maintain plasma albumin at normal concentrations postsurgery. The two gelatin preparations, Haemaccel and Gelofusine, maintained plasma viscosity. All three colloids led to a transient increase in activated partial thromboplastin time postsurgery and also a transient fall in the concentration of factor VIII, which were accompanied by a transient increase in bleeding time, but there was no measurable increase in blood loss. Inhibition of platelet aggregation by certain colloids may provide additional protection against the increased thrombotic risk in patients following major surgery.

Can the effects of clinical reperfusion fluids on platelet aggregation in vitro predict the effects of administration of such fluids in a clinical study ex vivo?

Reperfusion fluids are administered routinely during surgical operations and following trauma. Studies performed wholly in vitro have indicated effects of some fluids on haemostasis through inhibition of platelet aggregation. Recently we performed a study to further evaluate the effects of reperfusion studies in vitro and also a study in a clinical setting to determine the extent to which the results of in vitro experiments can be extrapolated to the clinical situation. The results indicate that a combination of homeostatic and trauma response mechanisms complicate the ability to extrapolate from the findings in vitro.

Scrotal pain in the absence of torsion; need for vigilance

Epididymitis is a common presentation of acute testicular pain seen in the emergency department, the differential diagnosis being testicular torsion. The vast majority of young men with epididymitis have an infective aetiology and this settle with antibiotic treatment. The clinical course of a patient who presented with testicular pain is described. At ultrasonography, the patient was found to have the uncommon condition of testicular microlithiasis, a condition that has been linked to malignant disease. Emergency doctors should be aware of the potential consequences of returning scrotal pain consistent with epididymitis to the community on antibiotic treatment alone. All patients with probable epididymitis should have either a scrotal ultrasound or specialist follow up.

Accidental hypothermia and active rewarming: the metabolic and inflammatory changes observed above and below 32 degrees C

OBJECTIVES

In accidental hypothermia the underlying physiological mechanisms responsible for poor outcome during rewarming through 32 degrees C remain obscure, although possible associations include changes in acid-base balance, divalent cations, and inflammatory markers. This study investigated the metabolic and inflammatory changes that occur during the rewarming of hypothermic patients.

METHODS

Eight patients, four men and four women, age 45 to 85 years, admitted with core temperatures <35 degrees C were included in the study. Patients were rewarmed with dry warm blankets and fluid replaced by crystalloid at 40 degrees C. Bloods for pH, ionised calcium (Ca(2+)) and magnesium (Mg(2+)), parathyroid hormone (PTH), interleukin 1 (IL1), interleukin 6 (IL6), tissue necrosis factor alpha (TNFalpha), were collected at presentation, during rewarming, and at 24 hours.

RESULTS

Four patients were admitted with mild (32 degrees -35 degrees C) and four with moderate (28 degrees -32 degrees C) hypothermia. Rewarming to 32 degrees C had no significant effect on the presenting acidosis (p=0.1740), although above 32 degrees C pH increased with temperature (p<0.0001). There was a negative correlation between pH and both Ca(2+) (p=0.0005) and Mg(2+) (p=0.0488) below 32 degrees C; above this temperature the relation was significant only for Ca(2+) (p=0.0494). PTH and Ca(2+) correlated positively (p=0.0041) and negatively (p=0.0039) below and above 32 degrees C respectively. There was no relation between IL1 or TNFalpha with Ca(2+) during rewarming, but IL6 and Ca(2+) correlated positively (p=0.0039) and negatively (p=0.0018) when presentation temperature was below and above 32 degrees C respectively.

CONCLUSIONS

During rewarming pH remains unchanged until patient temperature approaches 32 degrees C. Ca(2+) and Mg(2+) decline is associated with the pH increase above 32 degrees C. Poor outcome is associated with presentation temperature (<32 degrees C), non-physiological correlation between IL6-PTH-Ca(2+), and age (>or=84 years).

The Scottish doctor--learning outcomes for the medical undergraduate in Scotland: a foundation for competent and reflective practitioners

This paper describes a set of learning outcomes that clearly define the abilities of medical graduates from any of the five Scottish medical schools. The outcomes are divided into 12 domains that fit into one of three essential elements for the competent and reflective medical practitioner.

Structure and properties of a dimeric N-terminal fragment of human ubiquitin

Previous peptide dissection and kinetic experiments have indicated that in vitro folding of ubiquitin may proceed via transient species in which native-like structure has been acquired in the first 45 residues. A peptide fragment, UQ(1-51), encompassing residues 1 to 51 of ubiquitin was produced in order to test whether this portion has propensity for independent self-assembly. Surprisingly, the construct formed a folded symmetrical dimer that was stabilised by 0.8 M sodium sulphate at 298 K (the S state). The solution structure of the UQ(1-51) dimer was determined by multinuclear NMR spectroscopy. Each subunit of UQ(1-51) consists of an N-terminal beta-hairpin followed by an alpha-helix and a final beta-strand, with orientations similar to intact ubiquitin. The dimer is formed by the third beta-strand of one subunit interleaving between the hairpin and third strand of the other to give a six-stranded beta-sheet, with the two alpha-helices sitting on top. The helix-helix and strand portions of the dimer interface also mimic related features in the structure of ubiquitin. The structural specificity of the UQ(1-51) peptide is tuneable: as the concentration of sodium sulphate is decreased, near-native alternative conformations are populated in slow chemical exchange. Magnetization transfer experiments were performed to characterize the various species present in 0.35 M sodium sulphate, namely the S state and two minor forms. Chemical shift differences suggest that one minor form is very similar to the S state, while the other experiences a significant conformational change in the third strand. A segmental rearrangement of the third strand in one subunit of the S state would render the dimer asymmetric, accounting for most of our results. Similar small-scale transitions in proteins are often invoked to explain solvent exchange at backbone amide proton sites that have an intermediate level of protection.

Intramolecular addition of acyl radicals to alpha-substituted vinylogous carbonates: demonstrating the effect of ring size on acyclic stereocontrol

The level of stereocontrol obtained in the reduction of the free radical derived from the intramolecular addition of an acyl radical to an alpha-branched vinylogous carbonate is dependent upon the ring-size of the cyclic ether.

Regioselective and enantiospecific rhodium-catalyzed allylic amination with N-(arylsulfonyl)anilines

[reaction: see text]. The regioselective and enantiospecific rhodium-catalyzed allylic amination of secondary allylic carbonates 1 with N-(arylsulfonyl)anilines provides a convenient process for the construction of arylamines 2. This method, in conjunction with ring-closing metathesis and radical cyclization reactions, allows the direct construction of biologically relevant pharmacophores as exemplified by the construction of dihydroquinoline and dihydrobenzo[b]indoline derivatives.

The role of a beta-bulge in the folding of the beta-hairpin structure in ubiquitin

It is known that the peptide corresponding to the N-terminal beta-hairpin of ubiquitin, U(1-17), can populate the monomeric beta-hairpin conformation in aqueous solution. In this study, we show that the Gly-10 that forms the bulge of the beta-turn in this hairpin is very important to the stability of the hairpin. The deletion of this residue to desG10(1-16) unfolds the structure of the peptide in water. Even under denaturing conditions, this bulge appears to be important in maintaining the residual structure of ubiquitin, which involves tertiary interactions within the sequence 1 to 34 in the denatured state. We surmise that this residual structure functions as one of the nucleation centers in the folding process and is important in stabilizing the transition state. In accordance with this idea, deleting Gly-10 slows down the refolding and unfolding rate by about one half.

An unusual case of subdural haematoma presenting to the accident and emergency department

A case of subdural haematoma associated with an intracranial arachnoid cyst is reported. The pathogenesis, clinical presentation and treatment options of intracranial arachnoid cysts is discussed.

Quantitation of minimal disease levels in chronic lymphocytic leukemia using a sensitive flow cytometric assay improves the prediction of outcome and can be used to optimize therapy

Previous studies have suggested that the level of residual disease at the end of therapy predicts outcome in chronic lymphocytic leukemia (CLL). However, available methods for detecting CLL cells are either insensitive or not routinely applicable. A flow cytometric assay was developed that can differentiate CLL cells from normal B cells on the basis of their CD19/CD5/CD20/CD79b expression. The assay is rapid and can detect one CLL cell in 10(4) to 10(5) leukocytes in all patients. We have compared this assay to conventional assessment in 104 patients treated with CAMPATH-1H and/or autologous transplant. During CAMPATH-1H therapy, circulating CLL cells were rapidly depleted in responding patients, but remained detectable in nonresponders. Patients with more than 0.01 x 10(9)/L circulating CLL cells always had significant (> 5%) marrow disease, and blood monitoring could be used to time marrow assessments. In 25 out of 104 patients achieving complete remission by National Cancer Institute (NCI) criteria, the detection of residual bone marrow disease at more than 0.05% of leukocytes in 6 out of 25 patients predicted significantly poorer event-free (P =.0001) and overall survival (P =.007). CLL cells are detectable at a median of 15.8 months (range, 5.5-41.8) posttreatment in 9 out of 18 evaluable patients with less than 0.05% CLL cells at end of treatment. All patients with detectable disease have progressively increasing disease levels on follow-up. The use of sensitive techniques, such as the flow assay described here, allow accurate quantitation of disease levels and provide an accurate method for guiding therapy and predicting outcome. These results suggest that the eradication of detectable disease may lead to improved survival and should be tested in future studies.

Exact algorithms for computing pairwise alignments and 3-medians from structure-annotated sequences (extended abstract)

Given the problem of mutation saturation in ancient molecular sequences, there is great interest in inferring phylogenies from higher-order types of molecular data that change more slowly, such as genomic organization and the secondary and tertiary structures of ribosomal RNA and proteins. In this paper, we define edit distances based on two representations of RNA secondary structure, arc annotation and hierarchical string annotation, and give algorithms for computing these distances on pairs of annotated sequences, aligning pairs of annotated sequences, and computing 3-median annotated sequences from triples of annotated sequences. The 3-median algorithms can be used as part of a well-known iterative heuristic for inferring phylogenies. All given algorithms are adapted from algorithms for computing longest common annotated subsequences of pairs of annotated sequences.

Performance assessment of the Gulmay D3300 kilovoltage X-ray therapy unit

A performance assessment was made of the Gulmay D3300 kilovoltage (combined superficial and orthovoltage) X-ray therapy unit. Results are presented for the key dosimetric beam parameters required for routine patient treatment. This unit is relatively new to the UK market and displayed similar properties to other existing equipment. Beam half-value layers were different from comparable published data, but were consistent with the actual values of external tube filtration employed. The applicator, system interlocks and dose monitor performance were satisfactory and the tube leakage was below the UK recommended maximum (air kerma rate 300 mGy h(-1) at 5 cm from the tube head). The variation of absorbed dose with stand-off distance from the applicator base followed the inverse-square law for all tested combinations of beam tube potential (kVp) and applicator, and the measured focus-to-surface distances were in acceptable agreement with the nominal values. A significant beam profile asymmetry was seen for field sizes greater than 10 cm at the upper tube potential (kVp) range (maximum ionization quotient 1.08), but this was an inherent property of the X-ray tube. The difficulties of obtaining percentage depth dose measurements are discussed, and it was concluded that the use of published data (appropriately verified) was acceptable. The methodology followed could form the basis of an acceptance and commissioning protocol. To address the relative lack of agreed standards for this type of equipment, performance test tolerances are proposed that are recommended for new installations.