Flow-injection determination of total ammonia and total carbon dioxide in blood based on gas-diffusion separation and with a bulk acoustic wave impedance sensor

A novel flow-injection (FIA) system, for the rapid and direct determination of both total ammonia (T[NH3]) and total carbon dioxide (T[CO2]) in clinical blood samples, has been developed. Samples were injected into a carrier stream of H2O, then emerged with a reagent stream, where the analyte was converted into a gaseous species and diffused across a PTFE gas-permeable membrane into an acceptor stream. The trapped NH3/CO2 in the acceptor was determined on line by a bulk acoustic wave (BAW) impedance sensor. At a through-put of 20 and 65 h(-1), the proposed system exhibited a linear frequency response up to 200 micromol l(-1) ammonium and 20 mmol l(-1) bicarbonate with a detection limit of 1.0 and 10 micromol l(-1), respectively. Results obtained for T(NH3) in serum and T(CO2) in plasma were in agreement with those obtained by the conventional glutamate dehydrogenase (GDH) method and gas-sensing electrode method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rate and potential interferents on the FIA signals were also discussed.     

Vesicoureteral reflux following transurethral resection of bladder tumors

Duodeno-gastric reflux measured in 18 patients without gastrointestinal complaints showed a wide variation of regurgitation rates. Duodeno-gastric reflux was significantly diminished during duodenal acidification. The effect was more intense and lasted longer after olive oil infused intraduodenally, leading practically to a closed pylorus.     

A new mechanism for lengthening the lifetime of hydrogenation catalysts

Intermetallic compounds with d-transition metals have been used as catalysts. XPS and AES studies and the magnetic properties of LaNi₅ and FeTi show that surface segregation occurs and that superparamagnetic Ni and Fe precipitates are formed at the surface, catalyzing the dissociation of molecular hydrogen. The catalytic activity of many intermetallic compounds can be explained by surface segregation and the formation of d-transition metal precipitates. Contaminants often drive the segregation, hereby prolonging the lifetime of the catalyst. We predict that FeTi can replace Fe-catalysts being more resistant to contaminants.     

Thresholds for ultrasonically induced lung hemorrhage in neonatal swine

The threshold for generation of lung hemorrhage in adult mice by pulsed ultrasound has been shown to be approximately 1 MPa at the surface of the lung (10-microseconds pulse and a carrier frequency of 2 MHz). This investigation used neonatal swine to determine if the findings for mice can be generalized to other species. After exploratory observations, the inverse sampling method was used in a primary study (22 animals, 88 exposure sites) to determine the threshold for lung hemorrhage in neonatal swine. The primary study was followed by a separate confirmation study (13 animals, 48 exposure sites), testing the conclusions of the first study and comparing damage at subthreshold levels with sham-exposed animals. A separate investigation explored the histological nature of tissue damage at suprathreshold levels. A 2.3-MHz focused transducer (10 microseconds at 100-Hz pulse-repetition frequency) was incremented vertically for a distance of 2 cm over the chest of the subject for a total exposure period of 16 min. Animals were euthanized and lungs were scored by visual inspection for numbers and areas of gross hemorrhages. The threshold level for hemorrhage was approximately 1.5 MPa peak positive pressure in water at the surface of the animal or, at the surface of the lung, 1.1 MPa peak positive pressure, 1 MPa fundamental pressure, 0.9 MPa maximum negative pressure, 25 W cm-2 pulse average intensity or a mechanical index of 0.6. These values are essentially the same as those reported for adult mice.     

The visual-preference technique in infancy: effect of number of stimuli presented upon experimental outcome

To examine the effects of the number of stimuli presented when the visual-preference technique is used to measure attention in infancy, 2- and 4-month-old infants were randomly assigned to 1 of 3 experimental conditions. In the first condition, infants were shown 3 different checkerboards using the single-stimulus visual-preference methodology; in the second condition, 4 checkerboards; and in the third condition, 5 checkerboards. Infants in both the 3- and 4-pattern conditions were able to order the patterns as predicted by scaling theory. However, there was a significant decrease in the number of infants in the 5-pattern condition who could do so. The results are discussed in terms of both their methodological and theoretical implications.     

Fine mapping of the Darier's disease locus on chromosome 12q

Darier's disease (DD) is an autosomal dominant genodermatosis characterized by epidermal acantholysis and dyskeratosis. We have performed genetic linkage studies in 10 families with DD (34 affected) by analyzing 14 polymorphic microsatellite markers. Our results confirm recent reports mapping the DD gene to chromosome 12q23-q24.1. Haplotype analysis of recombinant chromosomes in our families, along with previously reported data, narrow the location of the DD gene to a 5 cM interval flanked by the loci D12S354 and D12S84/D12S105. This localization allowed exclusion of two known genes, PLA2A and PAH, as candidate loci for DD. Three other gene loci (PPP1C, PMCH, PMCA1), mapping in 12q21-q24, remain potential candidates.