Rheology of Dense Suspensions under Shear Rotation.

Dense non-Brownian suspensions exhibit a spectacular and abrupt drop in viscosity under change of shear direction, as revealed by shear inversions (reversals) or orthogonal superposition. Here, we introduce an experimental setup to systematically explore their response to shear rotations, where one suddenly rotates the principal axes of shear by an angle θ, and measure the shear stresses with a biaxial force sensor. Our measurements confirm the genericness of the transient decrease of the resistance to shear under unsteady conditions. Moreover, the orthogonal shear stress, which vanishes in steady state, takes non-negligible values with a rich θ dependence, changing qualitatively with solid volume fraction ϕ and resulting in a force that tends to reduce or enhance the direction of flow for small or large ϕ. These experimental findings are confirmed and rationalized by particle-based numerical simulations and a recently proposed constitutive model. We show that the rotation angle dependence of the orthogonal stress results from a ϕ-dependent interplay between hydrodynamic and contact stresses.

Reactive thrombocytosis might contribute to chemotherapy-related thrombophilia in patients with lung cancer.

PURPOSE: Thrombotic risk is increased in patients with cancer and further potentiated by chemotherapy. We assessed whether early hemostatic alterations could represent a risk factor for thrombosis in patients undergoing chemotherapy for lung cancer. PATIENTS AND METHODS: Forty-nine patients receiving chemotherapy for unresectable, locally advanced, or metastatic lung cancer were included. Blood cell count, prothrombin time, partial thromboplastin time, fibrinogen, antithrombin, D-dimers, protein C, protein S, homocysteine, folates, vitamin B12, and activated protein-C resistance were measured at day 0, +7, +15, and +21 of the first chemotherapy cycle. Factor V Leiden and FII G20210A mutations were assessed. Follow-up of patients was prospectively performed for thrombosis during all chemotherapy treatment. Factor V Leiden and FII G20210A frequency were the same as in controls. RESULTS: Average basal levels of prothrombin time, partial thromboplastin time, antithrombin, protein C, protein S, folates, vitamin B12, and activated protein-C resistance were normal and remained stable during chemotherapy. Homocysteine, D-dimers, and fibrinogen basal levels were high but remained constant after chemotherapy. An average reduction in platelet count was recorded at day +14 in all patients after a striking increase (5.2-fold) at day +21 in the group of patients treated with gemcitabine (P < 0.001). Four thrombotic events were recorded. In all cases, thrombosis occurred within 10 days of the second or the following chemotherapy cycle with gemcitabine and cisplatin. One patient had Factor V Leiden heterozygous disease. CONCLUSION: Our findings exclude alterations of coagulation inhibitors or activation of disseminated intravascular coagulopathy/fibrinolysis as factors that induce chemotherapy-related thrombosis in lung cancer. The temporal relationship between thrombocytosis at the time of chemotherapy administration and the clinical onset of thrombotic events suggests that thrombocytosis plays a role in triggering thrombotic complications.

Hyperhomocysteinemia in patients with Cushing's syndrome.

We evaluated serum homocysteine concentrations and the C677T polymorphism of the gene encoding for methylene tetrahydrofolate reductase, a key enzyme for homocysteine metabolism, in 57 patients with Cushing's syndrome, 41 with active disease, and 16 in remission after successful surgery and 105 blood donors. The patients with active Cushing's syndrome had significantly higher serum homocysteine levels and lower folate concentrations than either the patients in remission or controls. The presence of a statistically significant difference in homocysteine concentrations among the three groups was confirmed after adjustment for confounding variables. In a multiple regression model, homocysteine levels were significantly associated with midnight serum cortisol levels (beta = 0.33, P = 0.01), which is the most sensitive marker of endogenous hypercortisolism, and serum folate levels (beta = -0.32, P = 0.02). The distribution of methylene tetrahydrofolate reductase genotypes was not different between patients and controls. In conclusion, active hypercortisolism is associated with hyperhomocysteinemia and reduced serum folate concentrations, whereas the patients in remission have homocysteine concentrations comparable with healthy subjects. Low serum folate concentrations do not fully account for the increase in homocysteine levels that are positively correlated with cortisol levels. Hyperhomocysteinemia may be key to the prothrombotic state and increased cardiovascular risk of Cushing's syndrome.

Pathogenesis of hyperferritinemia cataract syndrome.

Hereditary hyperferritinemia-cataract syndrome (HHCS) is an autosomal dominant disorder characterized by bilateral cataracts and increased serum L-ferritin, in the absence of iron overload. Under physiological conditions, ferritin synthesis is finely regulated at the translational level by iron availability. This regulation is achieved by the high-affinity interaction between cytoplasmic mRNA-binding proteins (iron regulatory proteins, IRPs), and mRNA stem-loop structures, known as iron responsive elements (IREs), located in the untranslated regions (UTRs) of the mRNAs. A single IRE is located on the 5' UTR of a series of genes involved in iron metabolism, like L-ferritin, and the binding IRE-IRPs represses these genes translation. The deregulation of ferritin production responsible of HHCS is caused by heterogeneous mutations in the iron regulatory element (IRE) of L-ferritin that interfere with the binding of iron regulatory proteins, disrupting the negative control of L-ferritin synthesis and causing the constitutive up-regulation of ferritin L-chains. The HHCS families originate from different countries of Europe and North America, suggesting that HHCS may be distributed widely throughout the world and not sporadic, whereas its prevalence remains to be established. The lens seems to be particularly sensitive to the increased amount of L-ferritin and the alteration of the proteic equilibrium in this tissue can be responsible of the cataract. In spite of the elucidation of the genetic basis, the genotype phenotype correlation is not clear. Recently, a study based on the thermo-denaturation profile and dissociation constant of the IRE-IRP complex performed for several mutated IREs has provided evidence for a possible correlation between heterogeneous IRE mutations and serum ferritin levels. On the other hand, the in vivo relevance of these conclusions has not been determined completely. A clinical variability among subjects sharing the same mutation, whether they belonged to the same family or not, has also been demonstrated. These findings suggest that, besides the L-ferritin IRE genotype, additional factors are likely to modulate the lens involvement and the rate of progression to severe cataract in HHCS patients.

C29G in the iron-responsive element of L-ferritin: a new mutation associated with hyperferritinemia-cataract.

Hyperferritinemia-cataract syndrome (HHCS) is a dominant disorder characterized by high serum ferritin and early onset of bilateral cataract. The disorder is caused by mutations in the iron-responsive element (IRE) of l-ferritin, which disrupt the postranscriptional control of l-ferritin synthesis. Here, we report a new (C>G) mutation which affects base 29 in the loop (c.-169C>G), previously unrecognized as essential for the stem loop stability. The mutation was identified in two members of an Italian family. Computer modeling and electrophoretic mobility shift assay (EMSA) confirm a decreased affinity of the C29G IRE for IRPs control proteins.

Onset of cataract in early infancy associated with a 32G-->C transition in the iron responsive element of L-ferritin.

UNLABELLED: We describe the onset of cataract in early infancy in a family with hereditary hyperferritinaemia-cataract syndrome. The two probands presented with isolated hyperferritinaemia and had developed cataracts at the age of 18 months. Two members of their family with high ferritin levels (1270-1450 microg/l) had suffered from cataract since childhood. The mutation responsible was a 32G-->C change in the lateral bulge of the stem structure of the iron responsive element of the L-ferritin subunit gene. Mutations at this level cause particularly high ferritin levels, whereas the age of cataract onset and its severity are controversial subjects. In our family, early ophthalmic examination ruled out the possibility that cataract was due to age-related persistence of high ferritin levels in the lens and suggested that other factors may modulate the phenotype. CONCLUSION: cataract may appear early in hereditary hyperferritinaemia-cataract syndrome and this syndrome should be suspected and ferritin levels measured in all cases of cataract in children, even when the onset is in early infancy.

Anemia and iron overload due to compound heterozygosity for novel ceruloplasmin mutations.

Aceruloplasminemia is a recessive disorder characterized by anemia, iron overload, and neurodegeneration, caused by the absence of ceruloplasmin (Cp), a multicopper oxidase important for iron export. Few patients homozygous for loss of function mutations of the Cp gene have been reported. We describe a 62-year-old white woman with heavy liver iron overload, diabetes, anemia, and neurologic symptoms. She was compound heterozygote for 2 novel mutations that result in the absence of hepatocyte Cp: an adenine insertion at nucleotide 2917 causing a truncated protein and a C-G transversion causing a glutamine-->glutamic acid substitution at position 146. Although rare in whites, aceruloplasminemia should be considered in the differential diagnosis of unexplained anemia associated with iron overload, because these features anticipate progressive neurologic symptoms. We propose that anemia, secondary to the impaired macrophage iron release, plays a major role in hepatic iron overload through increased absorption mediated by the erythroid regulator.