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At least 1,297 records · Page 72Linked to original sources
PubMed1990

Designing the user interface using rapid prototyping.

The aim of this study was to evaluate and improve the menu interface design of an existing expert system. The system provided expertise concerned with evaluating human response to environments and was implemented onto a computer with a simple tree menu system. Two laboratory based experiments were carried out in which alternative menu interface designs were developed rapidly and compared with the original design. User acceptance tests which incorporated objective and subjective measures were iteratively used to evaluate and improve the interface designs. The results of these experiments indicated that, for the particular system under study, a graphic based design which displayed 58 options divided into levels on a single screen was preferred by users over the original menu interface which displayed one menu at a time with seven options per screen. The final interface remains to be tested under field conditions.

Journal Article↗
PubMed1992

Performance on a prototype keyboard with ternary chorded keys.

Ten subjects learned to operate a ternary chorded keyboard which took them, on average, just over three hours. After an additional 10 h of use, they were inputting an average 70 characters/min with an accuracy of better than 97%. The individual performances were quite different and variable, but throughout rapidly improved. The experiments indicated that people are able to memorize 59 chords, and to execute them quickly, with surprising facility.

Journal Article↗
PubMed1987

[13N]-beta-phenethylamine ([13N]PEA): a prototype tracer for measurement of MAO-B activity in heart.

[13N]beta-Phenethylamine ([13N]PEA) was evaluated as a radio tracer for the measurement of mouse heart monoamine oxidase (MAO) activity in vivo. After intravenous administration, [13N]PEA was deaminated by MAO-B. 13NH3 formed thereby was taken up by amino acids and trapped in the heart. The relation between the radioactivity trapped in the heart and the enzyme activity was examined. The radioactivity in the heart 15 min after administration was reduced in a dose-dependent manner by pretreatment with a specific MAO-B inhibitor, l-deprenyl, but not with a specific MAO-A inhibitor, clorgyline. A linear correlation existed between the heart radioactivity level and the heart MAO-B activity (0-45%). [13N]1,1-d2-2-Phenethylamine (C6H5-CH2-CD2-13NH2, [13N]d2PEA), a modified tracer with less reactivity towards the enzyme, was tested similarly. This tracer possessed a higher sensitivity than [13N]PEA, and a wider range (0-85%) of MAO-B activity correlated linearly with the trapped radioactivity. These results indicate that [13N]PEA derivatives ([13N]PEA and [13N]d2PEA) can be useful radiotracers for noninvasive measurements of MAO-B activity in the human heart.

Ammonia↗
PubMed1990

Induction of hepatic cytochrome P-450 mediated alkoxyresorufin O-dealkylase activities in different species by prototype P-450 inducers.

The induction of cytochrome P-450-mediated alkoxyresorufin O-dealkylase activities by various xenobiotics was examined in liver from a variety of animal species in order to gain insights into the substrate specificities of the induced P-450s. We found that forms of cytochrome P-450 capable of mediating the O-dealkylation of the short-chain phenoxazone ethers methoxy-, ethoxy- and propoxyresorufin were highly induced by 3-methylcholanthrene-type inducers and by Aroclor-1254 in all species tested, although there were species differences in the relative turnover rates for the various substrates. For example, in hamster liver the turnover rates for the short-chain resorufin ethers decreased in the following order: methoxy greater than ethoxy much greater than propoxy, while in the rat liver almost the exact opposite order was observed: ethoxy = propoxy much greater than methoxy. In contrast, the degree of induction by phenobarbital-type inducers of isozymes catalyzing the O-dealkylation of pentoxy- or benzyloxyresorufin was highly species-dependent. Thus, F344/NCr rats, B6C3F1 mice and NZB rabbits showed the greatest (greater than 20-fold) induction of these activities, either by phenobarbital or Aroclor-1254, while Mongolian gerbils showed intermediate levels of induction and Syrian golden hamsters exhibited very low induction. In the Japanese quail, phenobarbital- or DDT-treatment resulted in minimal induction of pentoxy- or benzyloxyresorufin O-dealkylase activity, although significant induction of the latter activity occurred following treatment with 5,6-benzoflavone or with Aroclor-1254. Since substrate specificities of most enzymes can be rationalized based upon differences in the steric requirements at the enzyme active site, we employed molecular modeling techniques to calculate the molecular dimensions of the alkoxyresorufins. Surprisingly, the minimal energy conformations in vacuo of each of the resorufin ethers examined are essentially planar. However, alternative configurations, especially for the pentoxy- and benxyloxy-ethers, having greater three-dimensional bulk are also energetically possible.

Animals↗
PubMed1995

Induction of CYP2B1 mediated pentoxyresorufin O-dealkylase activity in different species, sex and tissue by prototype 2B1-inducers.

The induction of CYP2B1 mediated pentoxyresorufin O-dealkylase (PROD) activity by various xenobiotics was explored in liver, kidney and lung from a variety of animal species of both sexes, in order to gain insights into the substrate specificity of induced CYPs. Marked species- and sex-related differences in the inducibility of PROD activity by tested chemicals were observed, the mouse being always more responsive when compared to hamster or rat. Induction by sodium phenobarbital (NaPB) led to a conspicuous increase in all situations, up to approximately 38-fold in female rat and mouse liver, with the exception of hamster kidney where PROD activity was only slightly affected. Unexpectedly, both sodium barbital (NaB) and phorone (PHR) moderately induce CYP2B1 isoforms in rat, the extent being highest in female kidney (PHR, 14-fold increase) and male lung (NaB, 4.5-fold). The degree of induction was maximal in the liver with some exceptions occurring in male mice where NaB induced up to 46- and 115-fold increases in lung and kidney and PHR up to 115-fold in kidney. Minimal, although significant induction of PROD activity following treatment with trans-1,2-dichloroethylene (1,2-DCE) occurred in all situations with the exception of hamster kidney and lung. Therefore, caution should be exercised when using PROD activity as specific enzymatic assay to probe CYP2B1-like induction.

Animals↗
PubMed1980

Discriminative stimulus effects of prototype opiate receptor agonists in monkeys.

This study was performed to clarify the apparent differences in the cellular substrates mediating the discriminative stimulus effects of morphine and cyclazocine. Squirrel monkeys trained to discriminate between i.m. injections of saline and either morphine (3.0 mg/kg) or cyclazocine (0.1 mg/kg) in a two-choice avoidance paradigm were tested for stimulus generalization to ethylketocyclazocine and SKF 10,047, proposed agonists of receptors mediating the effects of cyclazocine. Both drugs completely mimicked the stimulus effects of cyclazocine but not those of morphine. Naltrexone (0.3 mg/kg) produced a 3-fold shift to the right of the cyclazocine dose-response curve but did not completely block the cyclazocine-like stimulus effects of either SKF 10,047 or ethylketocyclazocine. SKF 10,047 was a competitive antagonist at the receptors mediating the stimulus effects of morphine. These data are consistent with a multiple opiate receptor model, and provide further evidence that the stimulus effects of morphine and cyclazocine are subserved by different cellular substrates.

Animals↗
PubMed1990

Severin is a gelsolin prototype.

A number of Ca2(+)-activated actin filament severing proteins have been identified in eukaryotic cells of diverse lineages. Gelsolin and villin, with molecular mass of about 80-90 kDa, and severin and fragmin, with molecular mass of about 40 kDa, have been isolated from vertebrates and invertebrates, respectively. We report here a direct comparison of the functional properties of gelsolin and severin, and the finding that the actin filament severing activity of severin, like that of gelsolin, is inhibited by polyphosphoinositides. However, severin does not nucleate actin filament assembly as well as gelsolin. These characteristics are very similar to those ascribed to the NH2-terminal half of gelsolin, supporting the idea that they are evolutionarily related. Regulation of severin by polyphospholipids raises the possibility that it may participate in agonist-stimulated regulation of the actin cytoskeleton in Dictyostelium discoideum.

Actins↗