Calcium phosphate/calcium oxalate crystal association in urinary stones: implications for heterogeneous nucleation of calcium oxalate

PURPOSE: Most stones contain more than one type of crystals, and some combinations, such as calcium phosphate/calcium oxalate, are more common than others. Epitaxy between the crystals has been suggested to play a role in growth of such stones. The specific aim of this study is to investigate the involvement of calcium phosphate in crystallization of calcium oxalate. MATERIALS AND METHODS: Twenty calcium oxalate stones or stone fragments were examined using various microscopic techniques, including scanning, transmission and back-scattered electron microscopy. Similarly, calcium oxalate stones induced on a plastic foreign body implanted inside urinary bladders of laboratory rats were also investigated. Examination of the interface between calcium phosphate and calcium oxalate crystals was emphasized. RESULTS: Close association between crystals of calcium phosphate and calcium oxalate were found in both the human and rat stones. All crystals examined were associated with an organic matrix on the surface and contained copious amounts of organic material within the crystalline entities. Interface between the crystals also appeared to be occupied by organic matrix. CONCLUSIONS: Results of this and other studies from our laboratory indicate that epitaxy between various crystals, even though theoretically possible, appears unlikely in vivo. The appearance of specific crystalline combinations in stones is probably a result of the urinary environment being conducive for crystallization of those components. Heterogeneous nucleation of calcium oxalate is most probably induced by biological elements, including membranous cellular degradation products.     

Bryostatin 1 induces ubiquitin COOH-terminal hydrolase in acute lymphoblastic leukemia cells

It has been previously reported that Bryostatin 1 (Bryo1) induces differentiation of the human acute lymphoblastic leukemia (ALL) cell line, Reh, to a monocytoid B-cell stage. In this study we demonstrate that a novel protein, ubiquitin COOH-terminal hydrolase (UCH-L1), is associated with this differentiation. Reh cells were treated with 200 nmol/l of Bryo1 for 72 h and analyzed for changes in morphology, surface immunophenotype, acid phosphatase and terminal deoxynucleotidyl transferase. Protein patterns of the parent and differentiated cells, by two-dimensional polyacrylamide gel electrophoresis (2D PAGE), were studied. Bryo1-treated cells expressed morphologic, phenotypic and enzymatic features of the monocytoid B-cell stage. The UCH-L1 enzyme (MW-pl 34-5.3) was detected by 2 D PAGE in the differentiated, but not in parent cells. The presence of UCH-L1 in the Bryo1-treated cells was further confirmed by immunoblotting of 2 D PAGE using UCH-L1 polyclonal antibody. Ubiquitin expression was studied in parent and Bryo1-treated cells and was compared with 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated cells. Both agents, TPA and Bryo1, increased the level of ubiquitin expression as detected by flow cytometry. Sodium borohydride, an inhibitor of UCH-L1, inhibited the Bryo1-induced differentiating effect on Reh cells. To date, the mechanism by which Bryo1, exerts its B-cell differentiating effect is not fully understood. This study shows that UCH-L1 expression may play a major role in Bryo1-induced differentiation in pre-B-ALL.     

Progress and prospects of group-III nitride semiconductors

We review recent progress in the group-III nitride and related materials, and electronic and optical devices based on them. Blue and UV (e.g. ultra violet) emitters and detectors, and high temperature/high power electronics which has long been coveted are beginning to be realized either in the laboratory or in the commercial arena, due in part to the breathtaking progress made in the last few years in the art and science of GaN, InN, AlN and their salloys. With brief references to the historical aspect of the relevant developments, this review concerns itself primarily with the current status of wide bandgap gallium nitride and related semiconductors from both the materials and devices points of view. Following a discussion of the structural properties of these materials, their electrical and optical properties are described in detail. The available data on metal contacts, the properties of which are indeed very conducive for the devices mentioned, from the points of view of ohmic contacts and Schottky barriers, are elaborated on. Recent progress on processing issues such as etching are reviewed. The review then embarks on an indash;depth discussion and analysis of field effect transistors, bipolar transistors, light emitting diodes, laser and photo detectors.     

Reactive brazing of ceria to an ODS ferritic stainless steel

This research study shows that a ceria ceramic can be bonded to an ODS ferritic stainless steel (MA956) by reactive brazing using a Ag₆₈-Cu_27.5-Ti_4.5 interlayer. The ability to join these materials provides an alternative to the current ceramic interconnects used in the development of solid oxide fuel cells. Initial results show that the ceramic-metal bonds survived the bonding process irrespective of the degree of porosity within the ceria ceramic. Metallographic analyses indicate that a reaction zone formed along the ceria/braze interface, which was not only titanium rich, but also consisted of a mixture of copper oxides. When the ceramic-metal bonds were exposed to high bonding temperatures or when subjected to thermal cycling at 700°C, this reaction layer increased in thickness and had a detrimental affect on the mechanical strength of the final joints.     

Enhancement of computed tomography liver contrast using iomeprol-containing liposomes and detection of small liver tumors in rats

RATIONALE AND OBJECTIVES: We evaluated iomeprol-containing liposomes (Lipiom), a new contrast medium for computed tomography (CT) liver scanning, in an animal model of chemically induced hepatocellular carcinomas and other liver tumors in rats. METHODS: Liver tumors were induced by administration of carcinogens to rats, either 0.55% (w/w) 1'-hydroxysafrole in the diet or induction by 3'-methyl-4-diethylaminoazobenzene followed by promotion with carbon tetrachloride. CT scanning was performed 1-3 hr after intravenous injection of iomeprol-containing liposomes. RESULTS: After injection of iomeprol-containing liposomes at a dose of 70 mg of liposome-entrapped iodine per kilogram of body weight, the normal liver parenchyma showed a contrast enhancement, in Hounsfield units, of more than 60% over the control value before bolus. Liver tumors with no or few Kupffer cells were not enhanced and appeared as dark areas within the normal parenchyma. Tumors and pretumoral lesions devoid of Kupffer cells, as small as 3 mm in diameter, could be distinguished using this non-invasive method. CONCLUSION: CT liver scanning after injection of iomeprol-containing liposomes appears to be promising method for detecting liver tumors and focal liver lesions.     

Purification and renaturation of recombinant human lymphotoxin (tumour necrosis factor beta) expressed in Escherichia coli as inclusion bodies

High level expression of recombinant human tumour necrosis factor β (rh TNF-β) in Escherichia coli results in the formation of two portions of protein, namely soluble active protein and insoluble protein which is inactive and aggregates in the form of inclusion bodies (IBs). In this study, a procedure for purification and renaturation of rh TNF-β from inclusion bodies has been designed and verified experimentally with a product purity of more than 90% and a recovery of about 30%. The procedure includes washing of IBs with specific wash buffer (Triton X-100/EDTA/lysozyme/PMSF), their solubilization with 8 mol dm^?3 alkaline urea, purification with ion-exchange columns, refolding with renaturation buffer and finally concentration and desalination with an ultrafiltration membrane. The characteristics of the renatured protein were identical with those of purified protein from the soluble fraction as demonstrated by (1) SDS-PAGE, (2) cytotoxic activity on mouse L929 cells, (3) N-terminal amino acid sequence, and (4) gel filtration chromatography.     

Rheology of concentrated solutions of hyperbranched polyesters

The solution rheology of different generations of hyperbranched polyesters in N‐methyl‐2‐pyrrolidinone (NMP) solvent was examined in this study. The solutions exhibited Newtonian behavior over a wide range of polyester concentrations. Also, the relative viscosities of poly(amidoamine) (PAMAM) dendrimers in ethylenediamine were compared with those of the hyperbranched polyesters in NMP. Both types of dendritic polymers have relative viscosities that are exponential functions of their molar fraction in solution. The slopes of these relative viscosity curves show a linear relationship with respect to the generation number. PAMAM dendrimers have the greater slopes for each generation, reflecting their relatively larger intrinsic viscosity values.     

Proposal for st-Routing Protocol

A routing protocol chooses one of the several paths (routes) from a source node to a destination node in the computer network, to send a packet of information. In this paper, we propose a new routing protocol, which we call st-routing protocol, based on st-numbering of a graph. The protocol fits well in noisy environments where robustness of routing using alternative paths is a major issue. The proposed routing protocol provides a systematic way to retry alternative paths without generating any duplicate packets. The protocol works for only those networks that can be represented by biconnected graphs.     

Simulating program disturb faults in flash memories using SPICE compatible electrical model

Electrical simulation is an important tool that enables designers to evaluate different design alternatives and assess their performance. In memory technology, these tools are used to study the performance of different cell structures and implementations. In this paper we use such simulations to study the impact of defects on the performance of flash memory bitcells. In particular, using a device level simulator, we develop a SPICE compatible model to simulate the operation of a 1T flash bitcell. We then describe a fault injection technique that can be used, in conjunction with the model, to simulate faulty cell behavior. The model is used to simulate different defects in the oxide layer of the flash core memory element. The impact of defects on bitcell behavior under disturb and normal operations is investigated and evaluated. The model is demonstrated to be valuable to evaluate the appropriateness of the logic tests and stress tests used to detect such defects in flash memories.