Emergence of spatiotemporal dislocation chains in drifting patterns.

One-dimensional patterns subjected to counter-propagative flows or speed jumps exhibit a rich and complex spatiotemporal dynamics, which is characterized by the perpetual emergence of spatiotemporal dislocation chains. Using a universal amplitude equation of drifting patterns, we show that this behavior is a result of a combination of a phase instability and an advection process caused by an inhomogeneous drift force. The emergence of spatiotemporal dislocation chains is verified in numerical simulations on an optical feedback system with a non-uniform intensity pump. Experimentally this phenomenon is also observed in a tilted quasi-one-dimensional fluidized shallow granular bed mechanically driven by a harmonic vertical vibration.

Spatially modulated kinks in shallow granular layers.

We report on the experimental observation of spatially modulated kinks in a shallow one-dimensional fluidized granular layer subjected to a periodic air flow. We show the appearance of these solutions as the layer undergoes a parametric instability. Due to the inherent fluctuations of the granular layer, the kink profile exhibits an effective wavelength, a precursor, which modulates spatially the homogeneous states and drastically modifies the kink dynamics. We characterize the average and fluctuating properties of this solution. Finally, we show that the temporal evolution of these kinks is dominated by a hopping dynamics, related directly to the underlying spatial structure.

fMRI of the sensorimotor cortex in patients with traumatic brain injury after intensive rehabilitation.

For evaluating the patterns of brain activation in sensorimotor areas following motor rehabilitation, seven male patients diagnosed with TBI underwent an fMRI study before and after being subjected to motor rehabilitation. Six patients showed a reduction in the BOLD signal of their motor cortical areas during the second fMRI evaluation. A decrease in cerebellum activation was also observed in two patients. Newly activated areas, were observed in four patients after treatment. In addition, an increase in the activation of the supplementary motor area (SMA) following rehabilitation was observed in only one test subject. The findings show that motor rehabilitation in TBI patients produces a decrease in the BOLD signal for the sensorimotor areas that were activated prior to treatment. In addition, we observed the recruitment of different brain areas to compensate for functional loss due to TBI in line with the cortical reorganisation mechanism.

Front propagation sustained by additive noise.

The effect of noise in a motionless front between a periodic spatial state and an homogeneous one is studied. Numerical simulations show that noise induces front propagation. From the subcritical Swift-Hohenberg equation with noise, we deduce an adequate equation for the envelope and the core of the front. The equation of the core of the front is characterized by an asymmetrical periodic potential plus additive noise. The conversion of random fluctuations into direct motion of the core of the front is responsible of the propagation. We obtain an analytical expression for the velocity of the front, which is in good agreement with numerical simulations.

Additive noise induces front propagation.

The effect of additive noise on a static front that connects a stable homogeneous state with an also stable but spatially periodic state is studied. Numerical simulations show that noise induces front propagation. The conversion of random fluctuations into direct motion of the front's core is responsible of the propagation; noise prefers to create or remove a bump, because the necessary perturbations to nucleate or destroy a bump are different. From a prototype model with noise, we deduce an adequate equation for the front's core. An analytical expression for the front velocity is deduced, which is in good agreement with numerical simulations.

[Moderate hyperhomocysteinemia and atherothrombosis]. / Hiperhomocisteinemia moderada y aterotrombosis.

Elevated levels of plasma total hornocysteine are now accepted as an independent risk factor for premature atherosclerosis. Nutritional, environmental and genetic factors may contribute to increase the levels of homocysteine. The exact pathogenesis of vascular damage induced by homocysteine is still not completely understood. Various mechanisms have been proposed, including a significant prooxidative activity, a stimulation of smooth muscle cells proliferation and an endothelial dysfunction. Folate, pyridoxine and cyanocobalamin are important cofactors for homocysteine metabolism. In most cases, elevated homocysteine can be reduced by administration of vitamin supplements. It has not yet been demonstrated that reduction in mortality and morbidity can be achieved with these regimens. However, food supplementation with folic acid has been recommended for treatment or prevention of homocysteine-related disorders in the North American population. Appropriate clinical trials are needed to evaluate the effect of lowering moderate homocysteine levels on atherosclerosis.

Pregnancy loss and autoantibodies against phospholipid-binding proteins.

OBJECTIVE: To evaluate the relationship between antibodies against beta 2-glycoprotein I or prothrombin and pregnancy losses in women with antiphospholipid antibodies. METHODS: Women with antiphospholipid antibodies, (lupus anticoagulant and/or anticardiolipin antibodies), with (n = 41) and without (n = 61) a history of pregnancy loss were evaluated. Thirty-one out of the forty-one patients with pregnancy loss had early miscarriages (at less than 13 weeks) and ten patients had late miscarriages. Immunoglobulin (Ig)-G and IgM anti-beta 2-glycoprotein I and anti-prothrombin antibodies were measured by an enzyme-linked immunosorbent assay method. RESULTS: A significant association between pregnancy loss and positive IgM anti-beta 2-glycoprotein I antibodies was found (odds ratio 2.6; 95% confidence interval 1.03, 6.6; P = .043). Women with late pregnancy loss had higher levels of both IgG and IgM anti-beta 2-glycoprotein I antibodies compared with controls (P < .05). There was a good correlation between anticardiolipin and anti-beta 2-glycoprotein I antibodies levels (IgG: r = 0.75; IgM: r = 0.73). In contrast, there was no correlation between the levels of anticardiolipin or anti-beta2-glycoprotein I antibodies and the levels of anti-prothrombin antibodies. Furthermore, the presence of anti-prothrombin antibodies was not associated with a history of pregnancy loss. CONCLUSION: The result of our study shows that there is a relationship between the presence of IgM anti-beta 2-glycoprotein I and previous miscarriages in women with anti-phospholipid antibodies.

[Antiphospholipid antibodies and cerebral ischemic infarction in a 6-year-old boy]. / Anticuerpos antifosfolípidos e infarto isquémico cerebral en un niño de seis años.

Lupus anticoagulant activity and anti-phospholipid antibodies (aPL) were found in a six-year-old child with cerebral ischemic infarction in the absence of any underlying disease. The association of these antibodies with thrombosis has been well documented in adult patients. In view of our observation, we believe that aPL may also be involved in the pathogenesis of arterial thrombotic events in childhood, and aPL should be systematically searched in these cases.

Placental alterations, intrauterine growth retardation and teratogenicity associated with enalapril use in pregnant rats.

Enalapril (15 mg/kg/day p.o.) was given to 11 pregnant rats from day 1 to 9 (E1-9) and to 11 rats from day 10 to 20 (E10-20) of pregnancy; 12 rats were the control group. Fifteen animals were sacrificed on day 20 of pregnancy and 19 were allowed to progress into partum. Placentas were smaller in E10-20 rats (-15%, p less than 0.05) and had a simple hypocellular cordonal structure; in E1-9 animals the predominant pattern was a combination of complex and simple structure. At day 20 the fetuses in the treated groups were smaller than the controls (-5% in E1-9 and -16% in E10-20, p less than 0.05); differences disappeared on the 13th day postpartum. Two fetuses from treated mothers presented incomplete skull ossification. We believe this report adds arguments to preclude converting enzyme inhibitors in pregnancy.

Inhibition of human platelet aggregation and thromboxane B2 production by melatonin. Correlation with plasma melatonin levels.

Plasma melatonin concentrations and the effect of melatonin on arachidonic acid (AA)-induced aggregation and thromboxane B2 (TxB2) production by platelet-rich plasma (PRP) were examined in five normal male volunteers, sampled at 2 hr intervals from 21:30 to 09:30 hr. Peak plasma melatonin concentration was found at 03:30 hr. Inhibition by 10(-6) M melatonin of AA-induced PRP aggregation was observed only in samples taken at 01:30 hr. Assessment of the inhibitory effect of 10(-9)-10(-6) M melatonin on AA-induced TxB2 production indicated that melatonin activity was greater at 01:30 h as compared to late night. Assessed as a global effect, the inhibitory activity of melatonin on PRP TxB2 showed a maximum at 01:30 hr and minimal effects at 03:30 hr, at the time when plasma concentrations of melatonin were highest. These results indicate the existence of a nocturnal variation in sensitivity of human platelets to melatonin, with a peak that precedes the maximum in circulating melatonin levels.

Clinical significance of various ELISA assays for detecting antiphospholipid antibodies.

We have compared the prevalence of antiphospholipid antibodies (APA) measured by enzyme-linked immunosorbent assay (ELISA), in 119 selected patients using five different antigens: bovine cardiolipin, phosphatidylserine, phosphatidylinositol, bovine partial thromboplastin and human brain partial thromboplastin. All the plasmas have been evaluated for the presence of lupus anticoagulant (LA) activity by clotting techniques. We found a significant association between the incidence of LA and APA (p less than 0.001), only moderate agreement between the prolongation of the activated partial thromboplastin time (APTT) and ELISAs (r around 0.50) and a good agreement between the ELISAs (r around 0.80). The combination of antibodies against cardiolipin (ACA) and human brain partial thromboplastin (AHPTA) allowed the detection of antibodies in most of the LA positive cases. ACA, AHPTA and antiphosphatidylinositol antibodies detected all the positive samples. Six patients (5%) had a single APA detected. The clinical associations of APA according to phospholipid specificity, immunoglobulin isotype and titer are shown.

Inhibition of human platelet aggregation and thromboxane-B2 production by melatonin: evidence for a diurnal variation.

The effects of melatonin on platelet aggregation and thromboxane-B2 (TxB2) production induced by 1-4 x 10(-6) M adenosine diphosphate (ADP) or 0.6 x 10(-3) M arachidonic acid (AA) were assessed in platelet-rich plasma (PRP). Micromolar concentrations of melatonin inhibited in a dose-dependent way ADP-induced platelet aggregation with individual inhibitions 40% or more at 10(-6)-10(-5) M. A significant depression of AA-induced platelet aggregation was observed only at 10(-5)-10(-4) M melatonin. Morning (0830 h)-evening (1800 h) studies of ADP-induced platelet aggregation in seven normal men showed a higher sensitivity at 1800 h when analyzed as a global inhibitory effect of melatonin (P less than 0.01). Moreover, only during the evening hours did melatonin induce reversible aggregation, an index of inhibition of the platelet secretory process elicited by ADP exposure. No diurnal variability in melatonin inhibition of AA-induced aggregation was detected. TxB2 production elicited by AA in the evening was inhibited significantly in a concentration-related manner by a 2-min preincubation with 10(-9)-10(-5) M melatonin, while during the morning hours the inhibition was significant only at 10(-6) M or higher melatonin concentrations. In the case of ADP, the inhibition of TxB2 release attained significance at 10(-5)-M (0830 h) or 10(-6)-M concentrations (1800 h). In the presence of either stimulatory agent, melatonin depression of TxB2 generation was about 2-fold greater at 1800 h than at 0830 h. The diurnal changes in melatonin effect on TxB2 production were also observed in thrombin-stimulated washed platelets. The present data indicate the existence of circadian variations in platelet responsiveness to melatonin in humans.

Comparison of various screening and confirmatory tests for the detection of the lupus anticoagulant.

Several assay systems have been proposed for detection of the lupus anticoagulant (LA). We compared several screening and confirmatory tests used for the detection of LA in 108 patients. LA was detected in 52 plasmas. The activated partial thromboplastin time (APTT) and the dilute Russell viper venom time (DRVVT) were the most sensitive screening tests as compared to the kaolin clotting time (p less than 0.001). The platelet neutralization procedure in both the APTT and DRVVT systems was superior to APTT performed with high phospholipid concentration (p less than 0.01) and tissue thromboplastin inhibition (p less than 0.001) as confirmatory tests. There was an association between the presence of LA and antiphospholipid antibodies detected by the enzyme-linked immunosorbent assay (p less than 0.001). In summary, our results show that APTT may be a sensitive test for the detection of LA when an appropriate reagent is employed, and that freeze-thawed platelets are more effective than phospholipids to neutralize LA activity.