Two time scales for self and collective diffusion near the critical point in a simple patchy model for proteins with floating bonds.

Using dynamic Monte Carlo and Brownian dynamics, we investigate a floating bond model in which particles can bind through mobile bonds. The maximum number of bonds (here fixed to 4) can be tuned by appropriately choosing the repulsive, nonadditive interactions among bonds and particles. We compute the static and dynamic structure factor (intermediate scattering function) in the vicinity of the gas-liquid critical point. The static structure exhibits a weak tetrahedral network character. The intermediate scattering function shows a temporal decay deviating from a single exponential, which can be described by a double exponential decay where the two time scales differ approximately by one order of magnitude. This time scale separation is robust over a range of wave numbers. The analysis of clusters in real space indicates the formation of noncompact clusters and shows a considerable stretch in the instantaneous size distribution when approaching the critical point. The average time evolution of the largest subcluster of given initial clusters with 10 or more particles also shows a double exponential decay. The observation of two time scales in the intermediate scattering function at low packing fractions is consistent with similar findings in globular protein solutions with trivalent metal ions that act as bonds between proteins.

Capillary attraction induced collapse of colloidal monolayers at fluid interfaces.

We investigate the evolution of a system of colloidal particles, trapped at a fluid interface and interacting via capillary attraction, as a function of the range of capillary interactions and temperature. We address the collapse of an initially homogeneous particle distribution and of a radially symmetric (disk-shaped) distribution of finite size, both theoretically by using a perturbative approach inspired by cosmological models and numerically by means of Brownian dynamics (BD) and dynamical density functional theory (DDFT). The results are summarized in a "dynamical phase diagram", describing a smooth crossover from a collective (gravitational-like) collapse to local (spinodal-like) clustering. In this crossover region, the evolution exhibits a peculiar shock wave behavior at the outer rim of the contracting, disk-shaped distribution.

Hydrodynamic interactions induce anomalous diffusion under partial confinement.

Under partial confinement, the motion of colloidal particles is restricted to a plane or a line but their dynamics is influenced by hydrodynamic interactions mediated by the unconfined, three-dimensional flow of the embedding fluid. We demonstrate that this dimensionality mismatch induces a characteristic divergence in the collective diffusion coefficient of the colloidal subsystem. This result, independent of the specific interparticle forces in the colloid, is solely due to the kinematical constraint on the colloidal particles, and it is different from the known divergence of transport coefficients in purely one or two-dimensional fluids.

Shock waves in capillary collapse of colloids: a model system for two-dimensional screened Newtonian gravity.

Using Brownian dynamics simulations, density functional theory, and analytical perturbation theory we study the collapse of a patch of interfacially trapped, micrometer-sized colloidal particles, driven by long-ranged capillary attraction. This attraction is formally analogous to two-dimensional (2D) screened Newtonian gravity with the capillary length λ as the screening length. Whereas the limit λ→∞ corresponds to the global collapse of a self-gravitating fluid, for finite λ[over ^] we predict theoretically and observe in simulations a ringlike density peak at the outer rim of a disclike patch, moving as an inbound shock wave. Possible experimental realizations are discussed.

Collective dynamics of colloids at fluid interfaces.

The evolution of an initially prepared distribution of micron-sized colloidal particles, trapped at a fluid interface and under the action of their mutual capillary attraction, is analyzed by using Brownian dynamics simulations. At a separation λ given by the capillary length of typically 1mm, the distance dependence of this attraction exhibits a crossover from a logarithmic decay, formally analogous to two-dimensional gravity, to an exponential decay. We discuss in detail the adaptation of a particle-mesh algorithm, as used in cosmological simulations to study structure formation due to gravitational collapse, to the present colloidal problem. These simulations confirm the predictions, as far as available, of a mean-field theory developed previously for this problem. The evolution is monitored by quantitative characteristics which are particularly sensitive to the formation of highly inhomogeneous structures. Upon increasing λ the dynamics shows a smooth transition from the spinodal decomposition expected for a simple fluid with short-ranged attraction to the self-gravitational collapse scenario.

Onset of anomalous diffusion in colloids confined to quasimonolayers.

It has been recently shown that a colloidal monolayer, e.g., formed at a fluid interface or by means of a suitable confining potential, exhibits anomalous collective diffusion. This is a consequence of the hydrodynamic interactions mediated by the three-dimensional (3D) ambient fluid when the particles are confined to reside on a two-dimensional (2D) manifold. We study theoretically and with numerical simulations the crossover from normal to anomalous diffusion as the particles are, in real systems, confined by a 3D external potential and thus have the possibility to fluctuate out of the 2D manifold, thus forming a quasimonolayer.

[Meningomyelitis disclosing Behçet's disease]. / Méningo-myélite révélatrice d'une maladie de Behçet.

The authors report a patient who developed a meningo-myelitis attributed to Behçet disease. Spinal MRI assessed spinal involvement. Among neurological manifestations of Behçet disease, isolated spinal cord involvement is infrequent. Dramatic improvement of neurological symptoms was obtained after steroid and immunosuppressive treatment.

[Estrogen and progestin receptors in meningiomas: a study in 22 cases (author's transl)]. / Récepteurs d'oestrogènes et de progestérone dans les méningiomes. Etude de 22 cas.

The authors have searched for oestrogene (RE) and progesterone (RP) receptors in 22 cases of meningiomas. Hormone receptors were determined on the cytosol and nuclear fractions of tumor tissues, using synthetic oestrogen R 2858 and progestin R 5020 in conditions where exchange was nearly achieved. The receptors were considered as present for values equal or higher than 100 femtomoles per gram of tumour tissue (fmol/gT). For the 22 studied cases the RE were present in 13 cases (59 p. 100) with values between 100 and 500 fmol/gT in 9 cases and higher than 500 fmol/gT in 4 cases. The RP were present in all cases (100 p. 100), with values between 100 and 500 fmol/gT in one case, between 500 et 5 000 fmol/gT in 13 cases and higher than 5 000 fmol/gT in 8 cases. The results were compared with neuropathologic data obtained by light microscopy. The clinical and biological significance of results are discussed.

[Early manifestations of neuromeningeal syphilis. Review of the literature apropos of 3 severe forms]. / Manifestations précoces de la syphilis neuro-méningée. Revue de la littérature à propos de 3 formes graves.

We report 3 cases of severe syphilitic neuro-meningitis during the secondary stage: acute transverse dorsal myelitis with permanent paraplegia in a 17 year old teenager (case no. 1), uveo-meningitis with intracranial hypertension and diminished vision in a 52 year old woman (case no. 2), lower medulla lesion in a 46 year old man (case no. 3). The diagnosis was based upon highly positive serological tests for syphilis, associated with a compatible clinical context and meningitis in CSF specimens. Treatment was successful in cases nos. 2 and 3, unsuccessful in case no. 1 due to the irreversible character of the medullar lesions. Based on these 3 cases, the following points are discussed: the relatively atypical clinical character in the current context, the difficulties of the diagnosis, and the treatment regimens recommended for neurological syphilis. Despite the rarity of such cases, their extreme severity early in the secondary stage strongly implies the necessity for prevention by detecting and treating early syphilis. Attention is drawn upon the importance of doing serological tests for syphilis when presented with any atypical neurological situation.

[Ependymoma of the cauda equina presenting as raised intracranial pressure without ventricular dilatation. One case (author's transl)]. / Ependymome de la queue de cheval révélé par une hypertension intra-crânienne sans dilatation ventriculaire. Une observation.

Intracranial hypertension is a rare phenomenon in the development of intra-spinal neoplasm. In the present case, it occurred without ventricular dilatation raising the problem of the underlying mechanism. Perturbations in the CSF reabsorption would appear less likely than an increase in brain volume, where cerebral edema may play an important role.

[Muscular metastasis, first symptom of bronchial carcinoma (author's transl)]. / Métastase musculaire révélatrice d'un carcinome bronchique indifférencié.

One case of bronchial carcinoma in which a muscular metastasis was the presenting symptom is reported. Clinical features included pain and gradual swelling of left musculus supra-spinatus. Surgical biopsy showed intra-muscular metastasis of bronchial origin. Radiotherapy provided transient pain relief, but the patient died 15 months after the first symptoms. Metastatic tumors of skeletal muscles are found in some cases, when carefully searched for in routine autopsy surveys. Most of these tumors remain asymptomatic; in other cases clinical picture includes pain, swelling and diffuse or nodular induration of the involved muscles. Biopsy shows metastatic tumor in these muscles, which generally retains the same growth pattern as seen in the primary tumor.

[Progressive dialytic encephalopathy. Role of the aluminium and neurological study. One case (author's transl)]. / Encéphalopathie progressive des dialysés: rôle de l'aluminium et étude neuropathologique. Une observation.

Report a typical case of dialytic dementia in a patient treated with aluminium gels. The course was fatal in fifteen months duration. Before interruption of aluminium gel intake, the aluminium blood level measured by atomic absorption spectrography was at 1300 microgram/l (normal less than 40 microgram/l). Cerebral aluminium was studied by the method of Le Gendre and Alfrey. On the three studied specimens of gray matter including, the parieto rolandic cortex, the thalamus, the cerebellar cortex, the mean aluminium concentration was seven times higher than the witness. The optic and electronic microscopy study showed important accumulation of lipofuscin. No neurofibrillary degeneration was observed. In contrast to the intensity of the clinical signs and the fatal course the cerebral lesions were slight.

[Hypothalamic form of Whipple's disease. Favorable effect of rifampicin]. / Maladie de Whipple à forme hypothalamique. Effet favorable de la rifampicine.

An unusual case of Whipple's disease is reported. The diagnosis was difficult as the characteristic digestive sign and symptoms (malabsorption, diarrhea, mucosal infiltration by PAS-positive macrophages) were absent. After a ten-year history of seronegative arthritis, myocardiopathy, with aortic insufficiency, basilar pulmonary infiltrates, enlarged lymph nodes, the patient, a 56 years old man, was referred to us for a severe vegetative and neurological dysfunction: stupor, dysarthria, akinesia, hypertonia, hypothermia and abnormal thirst. A CT-scan showed a low-density area of the right hypothalamus, and PAS-positive macrophages were found in a lymph node, in the CSF and in a cerebral biopsy. The patient then received a classical antibiotic treatment, yet the neurologic dysfunction remained severe. Finally, a trial with rifampicin brought a striking improvement of the patient's condition, which has now lasted for three years.

[Prolonged and reversible encephalopathy in a chronic haemodialysis patient. Probable responsibility of aluminium salts (author's transl)]. / Encéphalopathie prolongée et réversible chez un dialysé chronique. Responsabilité probable des sels d'aluminium.

A case of encephalopathy with elevation of plasma aluminium level in a patient treated by maintenance hemodialysis is reported. Clinical symptoms were made of moderate impairment of intellectual functions and of intermittent drowsiness. EEG after 3 minutes of hyperpnea evidenced bisynchronous anteriorly dominant intermittent delta waves. Plasma aluminium level, determined by atomic absorption spectrophotometry, was initially at 300 microgram/l (normal range greater than 40 microgram/l). After interruption of aluminium gels, clinical and EEG symptoms slowly subsided in 9 months, plasma aluminium level came down to 145 microgram/l. This picture of encephalopathy could preceede irreversible dialysis dementia in chronic dialysis patients.

[Pseudo-tumoral human African trypanosomiasis due to Trypanosoma gambiense. Clinical and tomodensitometry study (author's transl)]. / Formes pseudo-tumorales de la trypanosomiase africaine à Trypanosoma gambiense. Etude clinique et tomodensitométrique.

The authors report an observation of african trypanosomiasis due to Trypanosoma Gambiense, clinical signs included massive and progressive hemiplegia, papillary edema and vascular shift from median line at arteriography. These pseudo tumoral clinical features are unusual in this disease. Asymetrical heterogenous hypodensities of the centrum semioval are dominant in the initial CT scanner aspect. The confrontation of CT scanner images to the clinical and evolutive data suggests the presence of associated cerebral edema and demyelination. With treatment, hypodensities were regressing while images of subcortical atrophy appeared. Lastly, in spite of severe general signs and the importance of neurological deficit, arsenical treatment associated with high doses of corticotherapy lead to a rapid improvement.

[Intermittent claudication disclosing amyloidosis in a chronically hemodialysed patient with light-chain myeloma]. / Claudication intermittente révélatrice d'une amylose chez un hémodialysé chronique porteur d'un myélome à chaînes légères.

The occurrence of amyloid deposits in skeletal muscle and its vessels has been noted from a long date in amyloidosis. However, their clinical manifestations have been seldom noticed. The authors report the case of a patient with light-chain myeloma in which an arterial intermittent claudication led to the discovery of muscle vascular amyloid deposits. Muscle signs and symptoms due to amyloidosis and their mechanisms are reviewed.

[Reversible dialytic encephalopathy after interruption of aluminium intake. 6 cases (author's transl)]. / Encéphalopathie réversible des dialysés après arrêt de l'apport d'aluminium. 6 cas.

The cases presented with psychic troubles and repeated somnolence episodes accompanied by dysarthria in 5 cases, myoclonic jerks in 4 cases and epileptic seizures in 1 case. In all cases the EEG was disturbed. It showed symetrical, paroxystic, bilateral, monomorph slow activity with more or less frequent paroxysms. The average serum aluminium level was at 407 microgram/l in the acute phase, at 161 microgram/l in the remission phase and at 123 microgram/l three months later. After interruption of oral and dialytic aluminium intake the remission is maintained. However in 2 cases the transitory readministration of aluminium gel was followed by reversible recurrency. The role of both aluminium gel and dialysate aluminium as the origin of encephalopathy is discussed.