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PubMed2002

Photoinduced electron transfer from the excited J-aggregate state of a thiacarbocyanine dye to TiO2 colloids.

The photophysical properties of the J-aggregate of 3,3'-di(3-sulfopropyl)-4,5,4',5'-dibenzo-9-phenyl-thiacarbocyanine triethyl-ammonium salt in the absence and presence of TiO(2) colloids have been studied using UV-visible absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy, and ESR spectroscopy. The fluorescence emission of the J-aggregate decreases with increasing concentration of TiO(2) colloids. The average fluorescence lifetime of the J-aggregate in the presence of TiO(2) colloids is shorter than that in the absence of TiO(2) colloids. A strong photoinduced ESR signal has been observed during illumination by light with lambda=633 nm in the presence of TiO(2) and the ESR signal can be attributed to the J-aggregate radical cation. From the above results, it is concluded that photoinduced electron transfer from the excited singlet state of the J-aggregate to the conduction band of TiO(2) takes place and the electron transfer rate is about 1.5 x 10(8) s(-1).

Journal Article↗
PubMed1998

Effocacu and Significance of Sentinel Lymph Node Identification with Technetium-99m-labeled Tin Colloids for Breast Cancer.

PURPOSE: The sentinel lymph node (SLN) is thought to reflect the metastatic status of the remaining axillary lymph nodes in patients with breast cancer. We used technetium-99m-labeled tin colloids to identify SLN. The efficacy and significance of SLN identification using this method were investigated in terms of number, size, location, and tumor metastasis. The efficacy of the emulsion charcoalinjection method for the intraoperative visible identification of SLN was also evaluated. METHODS: Twenty-five patients with invasive breast cancer were studied. Underultrasonographic guidance, technetium-99m-labeled tin colloid particles (3 ml) were injected into 3 sites around the tumor within 3 mm of the margin or into the wall of the excisional biopsy cavity 2 hours before surgery. At surgery, just before the incision, an emulsion of charcoal particles (2.5 ml) was injected into 3 sites of the breast parenchyma surrounding the tumor. All patients underwent mastectomy with axillary dissection to the infraclavicular region. The radioactivity of each dissected lymph node was measured. All axillary specimens were processed in individual blocks for permanent section histopathologic evaluation with H & E. RESULTS: SLN were defined as lymph nodes with 100, 000 or more counts per minute (cpm) in radioactivity after injection of labeled tin colloids. In all 25 patients, SLN were identified (mean, 1.9 SLN/patient; range,1-4). Since the mean uptake in SLN was 383 124 cpm, but only 884 cpm in non-SLN nodes, discrimination between SLN and non-SLN nodes was easy. Clearly visible lymph nodes with charcoalstaining accounted for 83.3% of all SLN, although 21.3% of non-SLN also stained. SLN were located only in the axillary region, but there were no other specific features in the location or size of SLN. The SLN were metastatic in 10 of the 25 patients: in 4, the SLN were the only metastatic nodes whereas in the remaining 6 patients, other axillary nodes were also positive. Fifteen patients with no metastasis in SLN had no tumor involvement in any other lymph nodes. There were no skip metastases. CONCLUSION: SLN identified with labeled tin colloids have clinical value in predicting the metastatic status of the remaining axillary lymph nodes in breast cancer.

Journal Article↗
PubMed2006

Coexistence of colloid cyst and neuroglial heterotopia.

INTRODUCTION: Colloid cyst is a rare intracranial tumor in childhood. This is the first report on the coexistence of a colloid cyst and the neuroglial heterotopia. DISCUSSION: A 3-year-old boy presented with a 10-day history of headache. Radiological findings revealed a cyst in the third ventricle and a solid mass protruding into the lateral ventricle causing obstructive hydrocephalus. The cyst was attached to the solid mass. Endoscopic aspiration and removal of the cyst followed by biopsy of the protruding mass was performed. Headache and vomiting then disappeared and the patient returned to normal life. CONCLUSION: The pathologic diagnosis was a colloid cyst associated with neuroglial heterotopia. We experienced a case of coexistent colloid cyst and neuroglial heterotopia, which have different embryonal origins.

Brain Diseases↗
PubMed2006

Cooperative study by the Italian neuroendoscopy group on the treatment of 61 colloid cysts.

OBJECTS: Microsurgical resection, stereotactic aspiration and VP shunt have for years been the choice options for the treatment of colloid cysts of the third ventricle. Recently, endoscopic approaches have aroused increasing interest and gained acceptance. Although safer, this minimally invasive approach is considered less efficacious than microsurgery. Relatively long-term results are now available and some conclusions might be inferred on the usefulness of this procedure. MATERIALS AND METHODS: Between 1994 and 2005, 61 patients harbouring a colloid cyst of the third ventricle were treated with neuroendoscopic technique in 11 Italian neurosurgical centres. Cyst diameters ranged from 6 to 32 mm. A flexible endoscope was used in 34 cases, a rigid one in 21, both instruments in six. The technique consisted in cyst fenestrations, colloid aspiration, coagulation of the internal cyst wall and, occasionally, capsule excision. Mean postoperative hospital stay was 6.7 days. Early postoperative neuroimaging revealed a cyst residue in 36 cases (mean diameter 4.3 mm). There were two complications (3.2%). Follow-up varied between 1 and 132 months (mean 32 months, more than 5 years in 17 patients). There were seven asymptomatic recurrences, three of them evolving from a previous residue. CONCLUSION: The endoscopic approach to the treatment of colloid cysts is safe, effective and well accepted by patients. Although asymptomatic, recurrences (11.4%) cast a persisting shadow on the long-term results, and, therefore, the controversy with the traditional microsurgical treatment remains open.

Adolescent↗
PubMed1997

Histological and ultrastructural analysis of six colloid cysts in children.

Although colloid cysts of the third ventricle are unusual in children, we have recently encountered six examples. Histologically they were lined by cuboidal, pseudostratified or columnar ciliated and mucous-secreting epithelial cells. Two cases showed small microcysts within the fibrovascular stroma surrounding the main cyst. The outermost layer consisted of a glial-ependymal envelope, in keeping with the postulated supraventricular origin of colloid cysts. Scanning electron microscopy showed 10-40% ciliated cells, and no ballooning of non-ciliated cells. Aspiration of cyst contents was performed in three patients, two of whom subsequently required surgical resection 4 months and 8 years after drainage, respectively. In adults colloid cysts may be asymptomatic, whereas in children they have not been documented as incidental findings at autopsy. Two of our six cases died, both before a diagnosis was established. A colloid cyst of the third ventricle must be included in the evaluation of acute neurological deterioration in children, in whom they are more frequently lethal.

Adolescent↗
PubMed2005

Acute renal failure after overdose of colloidal bismuth subcitrate.

Bismuth salts are widely used to treat peptic ulcers. Acute toxicity with colloidal bismuth subcitrate overdose causes nephrotoxicity. There have been numerous reports of encephalopathy after long-term consumption of bismuth salts, but only a few cases of nephrotoxicity (adult and pediatric) have been documented to date. This report presents a case of acute renal failure due to colloidal bismuth subcitrate overdose in adolescent. A 16-year-old girl presented with complaints of nausea, vomiting, and facial paresthesia. Ten days earlier she had tried to commit suicide by taking 60 tablets of De-nol (colloidal bismuth subcitrate 18 g). The physical examination findings on admission indicated minimal fluid overload but no signs of encephalopathy. Laboratory tests on admission showed blood urea nitrogen 102 mg/dl, serum creatinine 19.9 mg/dl, and serum bismuth level 495 microg/l. The patient was started on appropriate fluid therapy and penicillamine as a chelating agent and then began hemodialysis on alternate days. The patient's renal function gradually returned to normal over 9 weeks and by 64 days after the overdose her serum bismuth level had fallen to almost half the level detected 2 days after admission. The patient made a complete recovery. The case demonstrates that acute renal failure can develop as a manifestation of acute toxicity from colloidal bismuth ingestion, and that the prognosis may be favorable if the patient receives appropriate supportive treatment and dialysis.

Acute Kidney Injury↗
PubMed2005

Endoscope-assisted removal of colloid cysts of the third ventricle.

Colloid cysts are benign space-occupying lesions, which arise from the velum interpositum or the choroid plexus of the third ventricle and are able to produce symptomatic obstruction of the foramina of Monro with resultant hydrocephalus. In our department, we have operated on colloid cysts routinely in an endoscope-assisted microsurgical manner via a key-hole approach. During a period of 10 years, 28 microsurgical resections of colloid cysts of the third ventricle were performed. Seven patients demonstrated colloid cysts inside the third ventricle with obstruction of the right foramen Monro, two patients demonstrated cysts with obstruction of the left foramen Monro. Twelve patients suffered from cysts inside the third ventricle with obstruction of both foramina Monro and five patients demonstrated cysts lying into the third ventricle without obstruction of the foramina. In 21 patients no preoperative therapy was performed outside. Three patients had received shunt systems before in other hospitals, two patients received aspiration of the cysts under stereotactic conditions and two patients received external ventricular drains. Total removal of the cyst was achieved in all patients (100%). No patient received a second operation, because none had a recurrent cyst. All cysts were removed with the cyst wall. Overall clinical improvement was achieved in a long-standing period between 6 and 83 months in 27 (96%) patients. In one patient (4%) the psychomotor disturbance was unchanged and no patient deteriorated. From the microsurgical point of view, the combination of keyhole surgery under endoscopic visual control using preexisting anatomical windows offers an effective minimally invasive approach.

Adolescent↗
PubMed2004

Colloid cyst headache.

Colloid cysts of the third ventricle are rare intracranial tumors, accounting for 0.5% of intracranial tumors. Colloid cysts represent 2% of gliomas, are more common in men than women, and usually are diagnosed between the third and fifth decades of life. The primary presenting complaint of this disorder is headache. The headaches are described as intermittent, severe and intense, and of short duration and usually are located frontally. The main associated features are nausea and vomiting. The headache can be relieved by lying down, which is unusual for headaches secondary to intracranial tumors. Colloid cysts of the third ventricle are diagnosed by computed tomography or magnetic resonance imaging and treatment is surgical. This rare type of headache disorder is significant because it is associated with sudden death. Recognition of the unusual features of colloid cyst headache may result in decreased mortality in this disorder.

Cerebral Ventricle Neoplasms↗
PubMed1988

Colloid osmotic pressure of cat brain homogenate separated from autogenous CSF by a copper ferrocyanide membrane.

The colloid osmotic pressure (oncotic pressure) of cat brain homogenate against cerebrospinal fluid (CSF) was determined using an electronic osmometer with a rigid selectively permeable copper ferrocyanide membrane. First, the basic characteristics of the membrane were examined. The relative value of the reflexion coefficient (sigma) for polyethylene glycol (PEG) became rather stable above a molecular weight of 6000 Da, below which sigma declined. The osmometer showed a linear response to sucrose concentration, whereas it revealed a non-idealistic change with respect to concentration of high molecules (PEG). The temperature effect on sigma for albumin solution was found to be large. The membrane could thus be used for measuring the relative value of the colloid osmotic pressure of protein solutions without dilution and at the same temperature as the calibrating solution. Samples of CSF and brain cortex were freshly obtained from 5 cats. The cortex was immediately homogenized and the colloid osmotic pressure of the homogenate against the CSF was measured at room temperature within 3 min after cortex removal. The mean value was 213 +/- 11 (S.D.) mm Hg with the osmometer calibrated with respect to the colloid osmotic pressure of autogenous plasma.

Animals↗
PubMed2005

Intraventricular colloid cyst, hydrocephalus and neurogenic stunned myocardium.

OBJECTIVE: To report the occurrence of neurogenic stunned myocardium in the context of a hydrocephalus due to a third ventricle colloid cyst. DESIGN: Case report. SETTING: Neurocritical care unit of a university hospital. PATIENT: The case of a 33-year-old woman with an intraventricular cerebral colloid cyst who developed hydrocephalus, cardiac arrest and survived is presented. Workup was consistent with neurogenic stunned myocardium in the context of acute hydrocephalus due to an intraventricular colloid cyst. RESULTS: The patient had decreased left ventricular ejection fraction, apex-sparing areas of hypokinesis and akinesis, wall motion abnormalities not matching a particular vascular territories, the peak troponin T level of 0.09 ng/ml and had normal coronary arteries at angiography. Seven days after the initial event the cardiac function recovered. Tumor resection was successfully performed. At 10 months after discharge, the only complaint was mild memory disturbance, she was completely functional with no evidence of seizures or of cardiac dysfunction. CONCLUSION: The sudden elevation of intracranial pressure, with the subsequent decreased cerebral perfusion pressure induces a vigorous cerebro-protective neuroendocrine system activation that can lead to the neurogenic stunned myocardium. Sudden death in patients with colloid cysts may be related to acute neurogenic cardiac dysfunction, and not necessarily cerebral herniation(s), as previously thought.

Adult↗
PubMed2004

On the origin of colloidal particles in the dispersion polymerization of aniline.

When aniline is oxidized in an aqueous medium in the presence of a steric stabilizer, colloidal polyaniline (PANI) dispersions are obtained. The generally accepted model of the stabilization assumes that the macromolecules of the water-soluble steric stabilizer are adsorbed at the polymer, precipitating during the dispersion polymerization, and provide steric protection against further aggregation. An alternative mechanism of conducting-polymer particle formation is proposed in the present study. We suggest that the steric stabilizer provides a site for adsorption of oligoaniline initiation centers; subsequent polymerization from anchored centers yields particle nuclei that grow to produce colloidal PANI particles. This hypothesis is based on the observation that the colloidal particles are obtained only in the case where the steric stabilizer is introduced in the early stages of polymerization when aniline oligomers are present in the reaction mixture. If the stabilizer had been added during the growth of PANI chains, colloidal dispersions would not have been produced. The process of particle growth is completely analogous to the formation of conducting PANI films on the surface of microparticles and various materials. There, the polymerization of aniline at the surfaces is preferred to the same process proceeding in the bulk of the reaction mixture. While the films grow at the interfaces with the reaction mixture, the dispersion particles similarly emanate from the stabilizer chains. The particle size, the formation of nonspherical morphologies, the importance of the chemical nature of the stabilizer chains, and the general relation between the conducting-polymer film and particle growth are discussed in the light of the proposed model.

Journal Article↗
PubMed2004

Macroporous Au materials prepared from colloidal crystals as templates.

In this paper, we reported the preparation of macroporous Au materials using organic colloidal crystals as templates and their catalytic activity for electroless copper deposition. The poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) copolymer colloids were deposited in an orderly manner onto the silicon surface, together with the infiltration of the Au nanoparticles into the interspaces of the colloids. The formed hybrid colloidal crystal subsequently was sintered at approximately 550 degrees C to remove the organic components fully to obtain a macroporous Au framework with three-dimensional ordered porous structure. The pore diameter was around 310 nm and almost monodisperse. It was demonstrated that the macroporous Au materials exhibit catalytic activity and can induce electroless copper deposition.

Journal Article↗
PubMed2005

The feasibility of inert colloidal processing of silicon nanoparticles.

Silicon nanoparticles have important applications, including nonvolatile floating-gate memory devices. To prevent device performance variations, particle size and oxide thicknesses need to be controlled with a high degree of precision. Additionally, producing well-ordered, two-dimensional arrays of nanoparticles may require the exploitation of self-assembly techniques and colloidal forces, which in turn requires that silicon nanoparticles first come into contact with liquids. Until recently, aerosol silicon nanoparticle collection into liquid was assumed to be an inert process. Once formed, the silicon nanoparticle colloid was assumed to be inert. In fact, silicon nanoparticles produced in the aerosol phase by dilute silane pyrolysis and size classified with a differential mobility analyzer undergo a size reduction upon collection in ethylene glycol, water, and ethanol. Unclassified polydisperse silicon aerosol nanoparticles with an average diameter of 11 nm become monodisperse when collected in a colloid and have a final particle diameter of 2-5 nm. Further evidence suggests that silicon nanoparticles collected in ethanol react with the ethanol to produce tetraalkylorthosilicate-like species. Collections of aerosol silicon nanoparticles in degassed water do not show measurable differences between the aerosol and colloidal size distributions. This reduced reactivity to the solvent indicates that the presence of dissolved oxygen in the solvent may be responsible for the reactivity between the silicon nanoparticles and the solvent.

Journal Article↗
PubMed2005

Preparation of ZnO colloids by aggregation of the nanocrystal subunits.

Colloidal ZnO particles with narrow size distribution were prepared via a sol-gel process by base-catalyzed hydrolysis of zinc acetate. The morphology of ordered arrays of the particles was recorded by SEM. SEM also reveals that these uniform particles were composed of tiny ZnO subunits (singlets) sized of several nanometers. The size of the singlets, which is confirmed by X-ray diffraction and UV-vis absorption spectra, increases as the aging time is prolonged. The size-selective formation of colloids by aggregation of nanosized subunits is proposed to consist of two-stage growth by nucleation of nanosized crystalline primary particles and their subsequent aggregation into polycrystalline secondary colloids. The aggregates are all spherical because the internal rearrangement processes are fast enough. The ZnO colloids, i.e., the aggregates, tend to self-assemble into well-ordered hexagonal close-packed structures. Room-temperature photoluminescence was characterized for green and aged ZnO.

Journal Article↗
PubMed2006

Gelation and internal dynamics of colloidal rod aggregates.

The internal dynamics of fractal cluster gels of colloidal boehmite rods with aspect ratios r = 3.9, 8.6, and 30.1, and colloidal polystyrene spheres (r = 1) are reported. Increasing r decreases the minimum colloid volume fraction for gelation. The behavior of the dynamic structure factor of rod gels is consistent with the internal dynamics of a constrained Brownian fractal object. Colloidal boehmite gels display an abrupt transition from floppy to brittle dynamics at phi approximately 10(-4). Moreover, the fractal cluster size of rod gels is not the determinant of the relaxation time of density fluctuations as it is in spherical particle gels. Instead, the relative behavior of the magnitude and time scale of the constrained fluctuations suggests that the fractal rod network is viscously coupled only on local, rather than cluster, scales. We hypothesize that noncentral forces between the anisometric particles are responsible for this anomalous behavior.

Journal Article↗
PubMed2006

A generalized model for the stability of polymer colloids.

A generalized model has been proposed to describe the stability of polymer colloids stabilized with ionic surfactants by accounting simultaneously for the interactions among three important physicochemical processes: colloidal interactions, surfactant adsorption equilibrium, and association equilibria of surface charge groups with counterions at the particle-liquid interface. A few Fuchs stability ratio values, determined experimentally for various salt types and concentrations through measurements of the doublet formation kinetics, are used to estimate the model parameters, such as the surfactant adsorption and counterion association parameters. With the estimated model parameters, the generalized model allows one to monitor the dynamics of surfactant partitioning between the particle surface and the disperse medium, to analyze the variation of surface charge density and potential as a function of the electrolyte type and concentration, and to predict the critical coagulant concentration for fast coagulation. Three fluorinated polymer colloids, stabilized by perfluoropolyether-based carboxylate surfactant, have been used to demonstrate the feasibility of the proposed colloidal stability model.

Journal Article↗
PubMed2005

Relative uptake of technetium 99m stannous colloid by neutrophils and monocytes is altered by gram-negative infection.

Gram-negative infection alters phagocytic cell function; hence, it could affect phagocytic uptake of inorganic colloids by these cells. Neutrophil and monocyte uptake of technetium 99m stannous colloid (99mTc SnC) in whole blood was measured in 10 patients with gram-negative infection (Burkholderia pseudomallei) and 7 controls. Mean uptake per individual neutrophil was reduced in infection. Uptake per monocyte was not significantly different. Blood from six normal individuals was incubated with lysed B. pseudomallei and colloid, which showed reduced neutrophil uptake, but increased monocyte uptake. These results indicate that uptake of 99mTc SnC stannous colloid can be used to measure alteration in phagocytic cell function. They suggest that infection with B. pseudomallei is associated with reduced phagocytosis by individual neutrophils, possibly through toxic effects of bacterial products. This could have immunopathogenic consequences for this gram-negative infection and may explain why it responds to granulocyte colony-stimulating factor.

Adult↗
PubMed2002

Energy of interaction in colloids and its implications in rheological modeling.

This work deals with the problem of deriving theoretical connections between rheology and interparticle forces in colloidal suspensions. The nature of interparticle forces determines the colloidal structure (crystalline order due to long range repulsive forces, flocculation due to attractive forces, etc.) and hence, the flow behavior of suspensions. The aim of this article is to discuss how these interactions enter the modeling of rheometric functions, in particular, the shear viscosity. In this sense, the main interactions commonly appearing in colloids are reviewed, as well as the role they play in phase transition behavior. Then, a series of approaches relating the interaction potential to viscosity is examined. The results of applying these models to experimental data are also discussed. Finally, examples of viscosity modeling for different interaction potentials are given, by using the structural model proposed previously by the authors. The possibility of relating the flow behavior of colloidal suspensions to the interaction between particles offers new perspectives for the study and technical applications of these systems.

Journal Article↗