Superconductivity in the Einstein solid VAl(10.1).

We used magnetic susceptibility, resistivity and heat capacity measurements to characterize the superconducting state in the Einstein solid VAl(10.1). We find that VAl(10.1) is a weak-coupling, type-II superconductor with T(c) = 1.53 K and an upper critical field of H(c2)(0) = 800 Oe. The heat capacity data in the range 0.07 K < T < 1.53 K are consistent with an isotropic energy gap of Δ(0) = 0.23 meV.

Drosophila female precopulatory behavior is modulated by ecdysteroids.

The effect of ecdysteroid signaling on Drosophila female precopulatory behavior was investigated using two types of mutants with either globally reduced ecdysteroid availability or reduced expression of ecdysone receptors in fruitless neurons, known to control sexual behavior. While being courted by males, mutant females performed significantly less full ovipositor extrusion behavior to reject male copulation attempts. Ecdysteroid depleted females (ecdysoneless(1)) performed male-like courtship behaviors, including unilateral wing extension and song production with patterns very similar to male courtship song. These results support the hypothesis that ecdysteroids modulate female sexual behavior, perhaps acting as a regulator of sexual motivation, and as a component affecting the performance of sex specific behavior patterns.

Drosophila male courtship behavior is modulated by ecdysteroids.

Temperature-dependent induction of ecdysteroid deficiency in the ecdysoneless mutant ecd(1) adult Drosophila melanogaster results in altered courtship behavior in males. Ecdysteroid deficiency brings about significantly elevated male-male courtship behavior including song production resembling that directed toward females. Supplementation with dietary 20-hydroxyecdysone reduces male-male attraction, but does not change motor activity, courtship patterns or attraction to females. These observations support the hypothesis that reduced levels of ecdysteroids increase the probability that male fruit flies will display courtship behaviors to male stimuli.

Unconventional T-H phase diagram in the noncentrosymmetric compound Yb2Fe12P7.

The temperature-(T-)magnetic-field (H) phase diagram for the noncentrosymmetric compound Yb(2)Fe(12)P(7), [corrected] determined from electrical resistivity (ρ), specific heat (C), and magnetization (M) measurements on single crystal specimens, is reported. This system exhibits a crossover from a magnetically ordered non-Fermi-liquid (NFL) phase at low H to another NFL phase at higher H. The crossover occurs near the value of H where the magnetic ordering temperature (T(M)) is no longer observable in C(T,H)/T and ρ(T,H), but not where T(M) extrapolates smoothly to T=0 K at a possible quantum critical point (QCP). This indicates the occurrence of a quantum phase transition between the two NFL phases. The lack of a clear relationship between the extrapolated QCP and NFL behavior suggests an unconventional route to the NFL ground states.

Superconductivity in heavy alkaline-Earth intercalated graphites.

We report the discovery of superconductivity below 1.65(6) K in Sr-intercalated graphite SrC(6), by susceptibility and specific heat (C(p)) measurements. In comparison with CaC(6), we found that the anisotropy of the upper critical fields for SrC(6) is much reduced. The C(p) anomaly at T(c) is smaller than the BCS prediction, indicating an anisotropic superconducting gap for SrC6 similar to CaC6. The significantly lower T(c) of SrC(6) as compared to CaC(6) can be understood in terms of "negative" pressure effects, which decreases the electron-phonon coupling for both in-plane intercalant and the out-of-plane C phonon modes. We observed no superconductivity for BaC(6) down to 0.3 K.

Esophageal injury from thoracic pedicle screw placement in a polytrauma patient: a case report and literature review.

The authors present a case report illustrating a visceral complication that may occur as result of thoracic pedicle screw placement. The case describes the previously unreported occurrence of esophageal impingement secondary to anterior vertebral body perforation by a pedicle screw at the third thoracic vertebra. This case highlights the challenge of thoracic pedicle screw placement and the importance of preoperatively measuring the maximum anterior-posterior dimension of the vertebral body.

Slow spin relaxation in a highly polarized cooperative paramagnet.

We report measurements of the ac susceptibility of the cooperative paramagnet Tb2Ti2O7 in a strong magnetic field. Our data show the expected saturation maximum in chi(T) and also an unexpected frequency dependence of this peak at low frequencies (<1 Hz), suggesting very slow spin relaxations are occurring. Measurements on samples diluted with nonmagnetic Y3+ or Lu3+ and complementary measurements on pure and diluted Dy2Ti2O7 strongly suggest that the relaxation is associated with dipolar spin correlations, representing unusual cooperative behavior in a paramagnetic system.

Bleeding time, stroke and myocardial infarction: the Caerphilly prospective study.

The stressed bleeding time is a simple 'global' test of haemostasis, dependent upon platelet function, rheology, thrombosis and intimal function. It could be of considerable value in clinical practice if it were shown to be predictive of vascular disease events. A stressed bleeding time test was done on 1319 men aged 55-69 years in the Caerphilly Cohort Study of Heart Disease, Stroke and Cognitive Decline. The men were followed-up and during the following 7-10 years 155 men had a myocardial infarction (MI) and 72 an ischaemic stroke. The mean bleeding time was 323 (SD 113)s. This was shorter in men who smoked by an average of 45 s, and lengthened in men who took aspirin daily by 40s. After making statistical adjustments for numerous possible confounding factors, the relative odds (ROs) of an MI within the third of men with the longest bleeding times, compared to the third with the shortest times, was 0.90 (0.40-2.03). For ischaemic stroke, the ROs in the third of men with the longest times were 1.42 (0.39-5.21). The stressed bleeding time does not predict either MI or ischaemic stroke. It has no place in health screening.

Platelet tests in the prediction of myocardial infarction and ischaemic stroke: evidence from the Caerphilly Prospective Study.

A platelet test that is predictive of myocardial infarction (MI) and/or stroke would enable the targeting of anti-platelet drugs towards high-risk patients. The predictive power of several platelet tests for MI and for stroke was examined in 2000 older men in the Caerphilly Cohort Study of Heart Disease, Stroke and Cognitive Decline. The tests were: aggregation to adenosine diphosphate (ADP) in platelet-rich plasma (PRP); aggregation to ADP in whole blood measured using an impedance method and a test of platelet aggregation induced in whole blood by high-shear flow. Around 200 MIs and 100 ischaemic strokes occurred during a 10-year follow-up. Neither primary nor secondary aggregation in PRP was predictive of MI. However, the fifth of men in whom the primary response to ADP was least, showed the highest risk of a subsequent stroke [relative odds (RO) 1.64; 95% confidence interval (CI) 1.12-2.43]. Aggregation in whole blood was not predictive of MI but, again, the fifth of men with the least platelet response showed the highest stroke incidence (RO 1.79; 95% CI 1.06-3.00). Retention of platelets in the high-shear test was not predictive of either event.

A comparison of von Willebrand Factor antigen with platelet activity in vitro in normal and venous occlusion blood.

Von Willebrand Factor (vWF) is essential for normal haemostasis involving platelet aggregation induced by high shear forces. In vitro a functional test of platelet aggregation using the filterometer is abnormal in von Willebrand's disease. However in normal people there is no significant correlation between the antigenic assay of vWF and the filter results. To study this discrepancy normal blood before and during venous occlusion, and blood before and after infusion of 1 deamino-(8-D-arginine) vasopressin was studied. During venous occlusion (VO) the increase in vWF due to the release of large multimers correlated precisely with the increase in the filterometer results. That this was due to the plasma vWF and not to any change induced in the platelets was shown as follows: The methodology was altered so that a small amount of the donor's platelet-poor plasma (PPP) was added to homologous normal substrate blood. The effect of the added donor's PPP was then shown to be closely correlated to the increase in the antigenic assay. Analysis of vWF multimer size showed during VO an increase in large multimers. We conclude that the effect of vWF on normal blood may be obscured by variation in platelet aggregability. In the filterometer system as elsewhere the large active multimers probably play a major part in causing platelet adhesion, aggregation and filter blocking. The filterometer test is influenced by the amount of vWF antigen, by the molecular size and activity of the vWF and by platelet sensitivity. Clinically this is a useful global test.

Defective von willebrand factor activity detected by the filterometer in three clinical conditions.

When exposed to high levels of shear in a filterometer, platelets bind to von Willebrand factor (vWF) via receptors Ib and IIb/IIIa, forming aggregates that block the filteromer. In this study we used the filterometer to explore the mechanisms by which abnormal vWF-platelet interaction might occur. In the first phase of the study, the global vWF-platelet interaction in native blood was investigated. In the second phase, to eliminate the difference that platelets might contribute, samples of platelet-poor plasma from test individuals were added to normal control blood and the mixtures were investigated by the filterometer. The filterometer results were adjusted for the antigen concentrations to obtain vWF potency ratios. Sodium dodecyl sulphate (SDS) agarose gel electrophoresis and SDS-Polyacylamide gel electrophoresis (PAGE) were used to analyze multimeric size and proteolytic profiles of vWF. Pregnancy was associated with high platelet retention, high vWF antigen concentration, normal multimeric size distribution, but decreased vWF potency ratios. The plasma samples of pregnancy contained one 183-kDa fragment not detected in normal plasma. These results suggested that in pregnancy, platelets were highly active. However, presumably due to abnormal proteolytic cleavage, vWF potency was decreased. This decrease in vWF potency might minimize the risk of thrombosis in association with highly active platelets. Renal transplant patients had normal platelet retention but high vWF levels. The plasma vWF contained normal multimers. A decrease in vWF potency, presumably caused by toxic inhibitors in the plasma, was detected. Aortic valve stenosis patients had decreased platelet retention, normal or slightly increased vWF antigen concentration and a decrease in large multimers. As a result, the vWF potency was markedly decreased. However, the results obtained with the filterometer became normal when the studies were repeated 3 months postpartum, when renal function had improved after transplantation, and when the aortic valves were corrected by surgery. These results indicate that the filterometer is a useful tool for elucidating the mechanisms by which vWF-platelet interaction might be impaired in various clinical conditions.

White cell retention compared with platelet retention in the filterometer: controls and abnormal states.

Platelets and white cells contribute to thrombus formation. In the filterometer, platelet retention in normal citrated blood increases from 47.5% at 0-5 s to 81.5% at 20-40 s. White cell retention is normally closely related to platelet retention at 0-5 s but less so at 20-40 s. However at 20-40 s the number of white blood cells (WBC) retained has decreased relative to 0-5 s. This apparent paradox is now further explored using antibodies to glycoprotein (GP) Ib, to von willebrand factor (vWf) and to GPIIb-IIIa together with observations on a number of clinical conditions with abnormal platelet retention. In citrated blood, platelet retention of 0-5 s was significantly decreased relative to normal in von Willebrand's disease, in aortic valve stenosis and with the addition of anti-vWf-GPIb and minimally with anti-GPIIb-IIIa antibodies. WBC retention of 0-5 s in these groups was always 41 2%. However when platelet retention 0-5 s was raised (pregnancy and venous occlusion), white cell retention was also raised. At 20-40 s in all the nine conditions studied, the white cell and platelet retention were closely related, but the percentage WBC retained decreased relative to the platelet retention. Granulocyte retention was higher than lymphocyte retention, but both cell types were similarly affected. We conclude that the platelets are retained as previously described. The white cells (all types) initially bind at least in part in an independent unexplained way (0-5 s). Thereafter the degree of platelet activity (retention %) largely determines the degree of WBC retention. This is probably due to a proportional amount of P-selectin liberated by the activated platelets.

Anti-glycoprotein Ib causes platelet aggregation: different effects of blocking glycoprotein Ib and glycoprotein IIb/IIIa in the high shear filterometer.

In 1987 we reported that when blood was forced through a fine filter under pressure in the filterometer the platelets aggregated and blocked the filter. von Willebrand factor (vWF) and glycoprotein (Gp) IIb/IIIa and calcium were involved. Results with anti-GpIb were equivocal. We now report that all the anti-GpIb antibodies studied, glycocalicin, as well as some concentrations of aurin tricarboxylic acid caused platelet aggregation in the pre-filter blood and therefore could not be used in the filterometer. Using two different molecules that prevent vWF binding to GpIb and two anti-GpIIb/IIIa antibodies at two pressures it has now been shown that GpIb, vWf and high shear are primarily responsible for platelet retention at 0-5 s. Progressive platelet retention studied between 20 and 40 s required high shear and GpIIb/IIIa after the calcium influx mediated by GpIb/vWF binding. When GpIb was inhibited, GpIIb/Ila could not function normally, so GpIb inhibition resulted in decreased aggregation both at 0-5 s and at 20-40 s. Anti-GpIIlb/IIIa caused a minimal decrease in retention at 0-5 s and marked inhibition at 20-40 s. These findings fit and amplify concepts derived from other high shear methodologies. A diagram is presented of the events leading up to the final 'passivation' of the 'thrombus' in the filter when the surface of the aggregated platelets becomes unattractive.

The relative power of heat-precipitation nephelometric and clottable (Clauss) fibrinogen in the prediction of ischaemic heart disease: the Caerphilly and Speedwell studies.

The Caerphilly and Speedwell studies have previously reported the predictive power of heat-precipitation, nephelometric, fibrinogen for 10-year incidence of ischaemic heart disease. A Clauss, clotting time, fibrinogen was also measured at baseline, but has not previously been reported. The predictive power of the two assays is compared. Both methods were employed on fasting blood samples from a total of 4391 men aged 45-63 years. Over the following 10 years 533 (12%) developed major ischaemic heart disease. Nephelometric fibrinogen was higher by 0.33 g/l among the men who developed disease; clottable fibrinogen was higher by 0.20 g/l. This difference is statistically significant (P=0.01). Relative odds of developing heart disease increased steadily to 3.53 (P<0.0001) in the 20% of men with the highest nephelometric fibrinogen; for clottable fibrinogen the corresponding relative odds increased to 2.24 (P<0.0001). When both measures of fibrinogen were included in logistic regression models together with age and smoking habit, the trend for incidence to increase with increasing nephelometric fibrinogen remained highly significant (P<0.0001), whereas for the Clauss fibrinogen the trend almost entirely disappeared (P = 0.37). We conclude that functional assays of clottable fibrinogen may not reflect all of the mechanisms which mediate the association between fibrinogen and cardiovascular disease and that assays of both 'heat precipitable' and 'clottable' fibrinogen should be included in all future prospective studies.

Platelet aggregation and incident ischaemic heart disease in the Caerphilly cohort.

BACKGROUND: Platelets are involved in myocardial infarction but evidence of prediction of infarction by measures of platelet function are sparce. METHODS: Platelet aggregation to thrombin and to ADP in platelet rich plasma was recorded for 2176 men aged 49-65 years in the Caerphilly cohort study. RESULTS: Results from 364 men were excluded, 80 of whom had not fasted before venepuncture; most of the others were excluded because antiplatelet medication had been taken shortly before the platelet tests. During the five years following the platelet tests 113 ischaemic heart disease (IHD) events which fulfilled the World Health Organisation criteria were identified--42 fatal and 71 non-fatal. No measure of platelet aggregation was found to be significantly predictive of incident IHD. The possibility that platelet function is predictive for only a limited time after it is characterised, and that prediction falls off with time, was tested. When IHD events are grouped by their time of occurrence after aggregation had been measured, the test results show a gradient suggestive of prediction of early IHD events. Thus, 24% of the men who had an event within 500 days of the test had had a high secondary response to ADP while only 12% of those whose IHD event had been 1000 or more days after the test had shown a high platelet response at baseline. The trend in these proportions is not significant. CONCLUSIONS: Platelet aggregation to thrombin and ADP in platelet rich plasma was recorded in the Caerphilly cohort study. No measure of aggregation was found to be predictive of IHD.

Platelets, aspirin, and cardiovascular disease.

Aspirin was first synthesised 100 years ago and its preparation and marketing is generally reckoned to have been the foundation of the pharmaceutical industry. For most of the time since then it has been used for the relief of pain and fever. The modern phase of aspirin use commenced with the reporting in 1974 of a randomised controlled trial in the secondary prevention of death by low-dose aspirin given to patients who had suffered a myocardial infarct. Reports of other trials followed and an overview of the first six trials was presented to the inaugural meeting of the Society for Clinical Trials in Philadelphia in 1980. There have been two further major overviews and the most recent, based on 145 trials, established that low-dose aspirin reduces vascular events by around one third. It has been estimated that, used appropriately, aspirin could prevent 100,000 premature deaths each year worldwide, at a cost of about 250 Pounds ($400) per life saved, and about 80 Pounds ($130) per cardiovascular event prevented. The evidence indicates that it is seriously underused at present. The aspirin story continues and trials are in progress to test other possible uses of aspirin, in vascular dementia, colorectal cancer, and cataract.

Sensitivity of aerobic spore-forming species of the genus Bacillus to the pteridine compound O129.

Discs containing the pteridine compound O129 at various concentrations may be useful in differentiating the following closely related species belonging to the genus Bacillus, viz. B. subtilis, B. licheniformis and B. pumilus; B. polymyxa and B. macerans; together with B. cereus and its subspecies B. cereus var. mycoides. At concentrations of 10 micrograms O129, the ATCC type strain of B. subtilis was resistant whereas B. licheniformis and B. pumilus were sensitive. However, B. subtilis was sensitive to O129 at 150 micrograms. Similar reactions differentiated the ATCC type strains of B. polymyxa and B. macerans. The ATCC type strain of B. cereus was resistant to O129 at both 150 micrograms and 10 micrograms, but its subspecies B. cereus var. mycoides (ATCC 28) was partially sensitive at 150 micrograms concentration. When clinical isolates of B. cereus var. mycoides were subsequently tested, this partial sensitivity was found to be a variable characteristic.