More sensitive high-pressure liquid-chromatographic determiantion of theophylline in serum

We present procedures for determining theophylline in 50 mul of serum. The drug is extracted into a small volume of solvent that contains an internal standard, 8-chlorotheophylline. The extract is Analyzed by isocratic reversedphase chromatography, with measurement of eluted theophylline at 273 nm. Day-to-day reproducibility within 5% is attainable for the concentration range 5--20 mg/liter. Other xanthines and related metabolites do not interfere. Sensitivity is 1 mg/liter. The correlation coefficient, when results by a spectrophotometric procedure were compared, was 0.989. Amobarbital, secobarbital, phenobarbital, and diphenylhydantoin do not interfere. Total analysis time for a single sample is 15 min.     

Ultrasound characterization of coronary artery wall in vitro using temperature-dependent wave speed

Temperature dependence of the speed of sound, /spl part/c//spl part/T, is examined as a parameter to characterize tissue-equivalent phantoms and coronary artery tissue in vitro. The experimental system comprises an ultrasound biomicroscope, operating at center frequency of 50 MHz, and a temperature controlled micropositioning sample cell. Radio frequency (RF) backscattered signals were recorded, with a digital oscilloscope, from 64 independent positions and at 5 temperatures starting at 31/spl deg/C (phantom) and 36/spl deg/C (tissue) in steps of one degree. Time shift per degree Celsius (/spl part/t//spl part/T) was obtained with a correlation technique applied between gated sections of two RF-signals collected with one degree temperature difference from the same location in the sample. The average , calculated for every position of the gated sections along the propagation axis of the ultrasound beam, has the slope proportional to the difference between the linear coefficient of thermal expansion and the thermal sensitivity of the speed of sound. Calibration measurements of /spl part/c//spl part/T, made with single- and three-layer tissue equivalent phantoms, correlated well (r/spl ges/0.91) with those measured by the time-of-flight substitution method. The /spl part/c//spl part/T was estimated for the three layers on the wall of eight samples of human coronary arteries, obtained at autopsy from four individuals. The /spl part/c//spl part/T for the intima layers decreases as the disease progresses from mild intimal thickening to a more advanced atherosclerosis.     

Results of radiation protection programmes on mammography

In this paper, we present the results of mammography quality control tests related to the work with Portuguese mammography equipment, either in conventional or in digital mammography computed radiography, showing the main differences in the tested equipments. Quality control in mammography is a very special area of quality control in radiology, which demands relatively high knowledge on physics. Digital imaging is changing the standards of the radiographic imaging. Regarding mammography, this is yet a controversial issue owing to some limitations of the digital detectors, like the resolution for instance. A complete set of results regarding radiation protection of the patients submitted to mammography diagnosis is presented. A discussion of the quality image parameters and its interpretation in conventional and digital mammography is presented. In conclusion, we present a sample of results that can be considered as characteristics of mammography equipment in Portugal.     

The influence of the tip structure and the electric field on BN nanocones

Different configurations for BN nanocones with 240° disclination are analysed through first-principles calculations based on the density-functional theory. The studied cone tips involve either four pentagons with two homonuclear bonds or two squares and two hexagons with no homonuclear bonds. The structures are both terminated by two three-coordinated atoms. Cohesive energy results show that the cone terminated in pentagons is slightly energetically preferred. The influence of a 1.7?V??(-1) external electric field, applied along the axis, on the structural changes and charge distributions is analysed. The responses of the charge distributions to the external electric field demonstrate the main role played by the B atoms for the applications of BN cones as probes in electronic microscopy as well as field emitters.     

Biomaterial with chemically engineered surface for protein immobilization

The last 3 decades have been a revolution in the area of sol-gel-derived materials. They can be used to encapsulate biomolecules such as enzymes, antibodies, hormones, and proteins retaining their functional state. Proteins can be immobilized in many ways but it is crucial that they retain their native conformational structure and, therefore, bioactivity. Porous silica gel matrixes with modified surfaces offer unlimited possibilities to control the protein-solid interaction behavior. The bioimmobilization process on sol-gel biomaterials with chemically engineered surface has driven applications on solid-phase materials, affinity chromatography, biosensors and many others. In the present work, we have aimed to produce surface-modified silica glass materials obtained via sol-gel route to be used as solid support on drug delivery systems and as solid-phase in immunodiagnostic. The functionalization process was carried out by reacting alkoxysilanes with 5 different silane surface modifying chemical groups: tetraethoxysilane (TEOS), 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltriethoxysilane (APTES), 3-glycidoxypropyltrimethoxysilane (GPTMS) and 3-isocyanatopropyltriethoxysilane (ICPES). The bioactivity assays were based on two main tests: (a) An in vivo bioresponse of rats with sol-gel disk implants with insulin protein incorporated. In vivo tests with adult male rats were used to verify the immobilized insulin bioactivity after implantation of different biomaterial with functionalized surfaces. All surface modified materials have presented hypoglycemic peak response associated with the insulin bioactivity. (b) The produced solid-phase sol-gel disks with protein substrates were tested through Enzyme Linked Immuno Sorbent Assay (ELISA). The immunoassay results have showed that glasses with chemically functionalized surfaces regulated the extent of bioimmobilization of protein. The amine, thiol and hydroxyl terminated porous gels have showed significant interaction with the antibody-antigen, during the coupling process. We believe that it is due to balance of forces associated with Van der Waals interaction, hydrophilic and hydrophobic forces and steric hindrance acting at the surface. Therefore, such novel biomaterial could be advantageously used in drug delivery systems and in immunoassays of diagnostic kits.     

Anodic linear sweep voltammetric analysis of Ni–Co alloys electrodeposited from dilute sulfate baths

Anodic linear sweep voltammetry was used to characterise electrodeposits of Ni, Co and five Ni–Co alloys (5:1, 2:1, 1:1, 1:2 and 1:5 ratios) obtained in a potentiodynamic mode on a vitreous carbon electrode from dilute sulfate baths. The voltammetric results showed a complex behaviour, with the deposits strongly dependent on the metal ion concentrations and less dependent on the final deposition potential. Probably due to simultaneous hydrogen evolution, the efficiency of the electrodeposition (in sulfate baths) and electrodissolution (in ammoniacal bath) processes of pure Co and Ni–Co alloys decreased with increasing final potential in all solutions, while that of pure Ni was enhanced with a shift to more negative potentials. Morphological information was acquired through investigations by techniques such as SEM, EDX and dot mapping. The voltammetric results revealed solid solution characteristics, with profiles varying from pure Ni to pure Co. The results of semi-quantitative EDX chemical analyses suggest a regular deposition mechanism instead of an anomalous one as is often observed in such binary systems.     

The preparation of field electron/field-ion emitters by ion etching

A new technique is described for the fabrication and resharpening of field emitters. This technique employs an ion gun and uses methods analogous to those used to produce thin foils for the transmission electron microscope. In this way it has proved possible to produce reliably sharp emitters of both metal and semiconducting materials and the technique is particularly useful when dealing with those materials normally difficult to electropolish or chemically etch. Applications lie not only in field electron emission and field-ion microscopy, but may also be relevant to the development of high current electron sources for use in electron microscopy.     

Determination of cell origin after marrow transplantation in canines by polymerase chain reaction and quantitation of the ZFY/ZFX genes

BACKGROUND: In order to follow the course of bone marrow engraftment in dogs, and to determine the presence, and percentage, of donor-derived cells in other canine tissues, a simple and fast method of determining cell origin after sex-mismatched bone marrow transplantation was developed. METHODS: Using universal primers, fragments from genomic DNA corresponding to ZFX and ZFY genes were amplified by polymerase chain reaction. A restriction fragment length polymorphism, combined with densitometric analysis, was then used to distinguish and quantitate ZFY and ZFX sequences. Unknown samples were analyzed against standards of known mixtures of male and female DNA. RESULTS: Canine ZFY and ZFX genes were clearly resolved after amplification, digestion with HaeIII, and denaturing polyacrylamide gel electrophoresis. Microchimerism could be detected in male and female dog DNA samples derived from a range of fresh and frozen tissues including spleen, testicle, and the central nervous system. The levels of chimerism determined using this method were in either agreement with results obtained by karyotyping or more sensitive, with a detection limit of 0.4% compared with 1-2%. CONCLUSIONS: Polymerase chain reaction/restriction fragment length polymorphism detection of the ZFY and ZFX genes was found to be simple, accurate, and reliable for assessing engraftment in dogs. When compared with cytogenetic analysis, this method was found to be faster to perform, more capable of detecting lower levels of microchimerism, and useful for detecting donor-derived cells in stored specimens and in tissues other than peripheral blood or bone marrow.     

Undiagnosed scleroderma in a patient with a difficult airway

BACKGROUND: We report one case of symptomatic aneurysm of infrarenal abdominal aorta in a patient symptomatic for acute abdomen. METHODS: The patient was accepted at the Emergency Care Unit and the routine admission tests were taken. US of the abdomen revealed a (SVI) disposition of the organs and an aneurysm of the abdominal aorta below the renal arteries. Patient underwent an aorto-aortic straight graft CONCLUSIONS: In this case-report we show SVI cannot be considered a problem in the surgical treatment of symptomatic abdominal aortic aneurysms.