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At least 1,423 records · Page 79Linked to original sources
PubMed1981

Digital scintigraphy: principles, design, and performance.

In a digital camera the position of a scintillation event is computed following analog-to-digital conversion of photomultiplier pulse charges. Digital position analysis is essentially a mathematical inversion procedure based upon calibrated responses of the photomultipliers to scintillations from a narrow-beamed source that maps a detector's field of view. Operationally, a camera's image characteristics are optimized by means of computer-generated inversion reference tables, individually tailored to the specific response characteristics of each detector. Design considerations indicate that cameras of varied configurations, e.g., linear, disc-shaped, rectangular, or cylindrical, can be analyzed by this method. Also, for any given electro-optical system, energy resolution, spatial characteristics, and event-rate performance can be made superior to analog systems. The measured performances of a one-dimensional test camera, although limited in its optical and electronic design, support this conclusion.

Analog-Digital Conversion↗
PubMed2003

Laparoscopic cholecystectomy for elderly patients: gold standard for golden years?

HYPOTHESIS: Laparoscopic cholecystectomy (LC) has known physiological benefits and positive socioeconomic effects over the open procedure. Although recent studies have questioned the technique's efficacy in elderly patients (>65 years), we hypothesize that LC is safe and efficacious in that patient group. METHODS: Five thousand eight hundred eighty-four consecutive patients (mean age, 40 years; 26% male) underwent an attempted LC (conversion rate, 5.2%) from 1991 to 2001 at a teaching institution. Of these, 395 patients (6.7%) were older than 65 years. Analysis included patient age, sex, American Society of Anesthesiologists classification, conversion rate, morbidity, mortality, and assessment of results over time. RESULTS: Elderly patients were predominantly male (64%). Septuagenarians had a 40% incidence of complicated gallstone disease, such as acute cholecystitis, choledocholithiasis, or biliary pancreatitis, and octogenarians had a 55% incidence. Overall mortality was 1.4%. The conversion rate was 17% for the first 5 years of the study period and 7% for the second half. The conversion rate was 22% for patients with complicated disease and 2.5% for patients with chronic cholecystitis. Average hospital stay decreased from 10.2 days to 4.6 days during the first and second half of the study period, respectively. CONCLUSIONS: The results of LC in patients aged 65 to 69 years are comparable with those previously reported in younger patients. Patients older than 70 years had a 2-fold increase in complicated biliary tract disease and conversion rates, but a low mortality rate (2%) compared with results of other authors (12%), despite an increase in American Society of Anesthesiologists classification. Increased technical experience with LC favorably affected outcomes over time. Early diagnosis and treatment prior to onset of complications are necessary for further improvement in the outcomes of elderly patients undergoing LC.

Aged↗
PubMed1999

Expression of p34(cdc2) and cyclins A and B compared to other proliferative features of non-Hodgkin's lymphomas: a multivariate cluster analysis.

In view of recent knowledge on proteins regulating the cell cycle, we re-evaluated proliferative features of 98 diffusely growing non-Hodgkin's lymphomas. The combined use of 5 proliferation-associated variables (mitotic indices and percentages of Ki-67(+), p34(cdc2+), cyclin A(+) and cyclin B(+) cells) and their entry into a multivariate cluster analysis separated, without overlaps, the entire cohort into 3 groups (clusters) with (1) low, (2) intermediate and (3) high proliferative activity. Conversely, bivariate plots exposed considerable cluster overlaps. Multivariate stepwise discriminant analysis of all cases revealed a decreasing order of discriminant power for % Ki-67(+) cells > % p34(cdc2+) cells > mitotic index > % cyclin A(+) cells > % cyclin B(+) cells. The combined use of 2 variables only, mitotic index and % p34(cdc2+) cells, allowed a clear-cut separation of clusters 2 and 3. In bivariate plots, correlations were best between % Ki-67(+) cells and % cyclin A(+) cells and between mitotic indices and % cyclin B(+) cells. Except for chronic lymphocytic leukemias, immunocytomas and marginal zone lymphomas (all in cluster 1), individual lymphoma entities were distributed among at least 2 clusters. There was, however, a marked preponderance of mantle cell lymphomas and diffuse follicular center lymphomas in cluster 1 and of diffuse large B-cell lymphomas and peripheral T-cell lymphomas in cluster 2. Anaplastic large-cell lymphomas predominated in cluster 3 and responded best to therapy.

Adolescent↗
PubMed2005

Topological analysis of GtrA and GtrB proteins encoded by the serotype-converting cassette of Shigella flexneri.

Serotype conversion (O-antigen glucosylation) in Shigella flexneri is mediated by temperate bacteriophages, which encode a three-gene cluster that contains gtrA, gtrB, and gtr([type]). Sequence analysis has revealed that gtrA and gtrB are conserved and readily interchangeable between serotypes. The gtr([type]) is unique in each serotype and responsible for specifically mediating conversion by the addition of a glucosyl group to the O-antigen units. Analysis of the GtrA and GtrB amino acid sequence using computer prediction programs indicated that GtrA and GtrB have four and two transmembrane segments, respectively. The topology model of GtrA was analyzed by constructing consecutive sandwich fusions using a dual reporter PhoA/LacZ at predetermined positions targeting each of the 3 cytoplasmic and 2 periplasmic hypothetical loops. The topology of GtrB was determined by constructing C-terminal truncated fusions of GtrB to full-length PhoA and LacZ by a PCR-mediated method. These approaches revealed that GtrA consists of four transmembrane segments with both the N-terminal and C-terminal ends in the cytoplasm. Accordingly, GtrB consists of two transmembrane segments with both ends also in the cytoplasm. Furthermore, membrane anchorage of the extended N-terminal end of GtrB was found to be important in catalysis. This study completes the topology of all three proteins (GtrA, GtrB, and the gtr([type]): GtrV) involved in the glucosyltransferase activity that results in serotype conversion of S. flexneri. A model is proposed showing how both O-antigen synthesis and modification take place in S. flexneri.

Aldehyde Oxidoreductases↗
PubMed1982

Study of the metabolic conversion of imipramine and desipramine to N-nitrosodesipramine by bacteria using a nitrogen-selective GC analysis.

A GC method using dual nitrogen selective and flame ionization detectors was developed for the determination of N-nitrosodesipramine using N-butyryldesipramine as the internal standard. The precision of the method was found to be +/- 5.0% and the accuracy was +/- 4.9%. The method could be used to detect 10 ng/ml of N-nitrosodesipramine in bacterial cultures. When desipramine and sodium nitrite were incubated with aerobic or anaerobic bacteria, the nitrosamine level was found to be 10-300 times higher than the controls. When imipramine and potassium nitrate were incubated with a mixed anaerobic culture, the level of N-nitrosodesipramine was found to be 4.5 times higher than the control.

Aerobiosis↗
PubMed1988

Quantitative conversion of diether or tetraether phospholipids to glycerophosphoesters by dealkylation with boron trichloride: a tool for structural analysis of archaebacterial lipids.

A method for preparing glycerophosphoesters from ether phospholipids by dealkylation with boron trichloride (BCl3) is described. Treatment of ether phospholipids in chloroform with BCl3 for 30 min at room temperature yielded almost quantitatively the corresponding glycerophosphoesters retaining the intact polar head group of the ether phospholipids. Thus, glycerophosphocholine, glycerophosphoinositol, glycerophosphoglycerol, glycerophosphoserine, glycerophosphate, and glycerophosphoethanolamine were prepared from the diether analogs of phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol, phosphatidylserine, and phosphatidic acid, and the tetraether analog of phosphatidylethanolamine, respectively. BCl3 also cleaved diacyl, alkyl-acyl, and alk-1-enyl-acyl forms of phospholipids to yield corresponding glycerophosphoesters. The glycerophosphoesters were separated more rapidly by cellulose thin-layer chromatography with the same solvent system as in paper chromatography. This method is of great use for structure determination of glycerophosphoester backbones of ether phospholipids, analogous to the mild alkaline methanolysis of diacyl form of phospholipids, as well as for the analysis of alkyl chains. It is, however, not applicable to glycolipids because of cleavage of glycosidic bonds by BCl3.

Archaea↗
PubMed2005

Inter- and intralocus recombination drive MHC class IIB gene diversification in a teleost, the three-spined stickleback Gasterosteus aculeatus.

The mutational mechanism underlying the striking diversity in MHC (major histocompatibility complex) genes in vertebrates is still controversial. In order to evaluate the role of inter- and intragenic recombination in MHC gene diversification, we examined patterns of nucleotide polymorphism across an exon/intron boundary in a sample of 31 MHC class IIB sequences of three-spined stickleback (Gasterosteus aculeatus). MHC class IIB genes of G. aculeatus were previously shown to be under diversifying (positive) selection in mate choice and pathogen selection experiments. Based on recoding of alignment gaps, complete intron 2 sequences were grouped into three clusters using maximum-parsimony analysis. Two of these groups had >90% bootstrap support and were tentatively assigned single locus status. Intron nucleotide diversity within and among loci was low (p-distance within and among groups = 0.016 and 0.019, respectively) and fourfold lower than the rate of silent mutations in exon 2, suggesting that noncoding regions are homogenized by frequent interlocus recombination. A substitution analysis using GENECONV: revealed as many intergenic conversion events as intragenic ones. Recombination between loci may explain the occurrence of sequence variants that are particularly divergent, as is the case in three-spined stickleback, with nucleotide diversity attaining dN = 0.39 (peptide-binding residues only). For both MHC class II loci we also estimated the amount of intragenic recombination as population rate (4N(e)r) under the coalescent and found it to be approximately three times higher compared to point mutations (Watterson estimate per gene, 4N(e)mu). Nonindependence of molecular evolution across loci and frequent recombination suggest that MHC class II genes of bony fish may follow different evolutionary dynamics than those of mammals. Our finding of widespread recombination suggests that phylogenies of MHC genes should not be based on coding segments but rather on noncoding introns.

Animals↗
PubMed2004

Taiwanese young adults' intergenerational communication schemas.

This study examined intergenerational communication schemas by investigating young adults' cognitive representations of communication with older adults in Taiwan. Forty-one Taiwanese college students described conversations with an older adult in response to a variety of interviewer prompts. Transcripts were read and content analyzed by the first two authors. To capture the characteristics of the conversation descriptions, eleven coding dimensions were generated based on schema theory, and all conversation descriptions were coded along these dimensions. Coding results were submitted to hierarchical cluster analysis, yielding five schemas: Mutually satisfying, helping, mixed feelings, small talk, and mutually unpleasant conversations. Results are discussed in terms of similarities and differences from Harwood, McKee and Lin's (2000) study, schema theory, intergenerational communication, and Chinese cultural norms.

Adult↗
PubMed2005

Enzymatic conversion-based method for screening cyclic dipeptide-producing microbes.

We developed a method for screening cyclic dipeptide-producing microbes by enzymatic conversion. In this method, cyclic dipeptides are detected by the combination of: (i) conversion of cyclic dipeptides to dehydro cyclic dipeptides by cyclo(Leu-Phe) oxidase and (ii) detection of the dehydro derivative by UV spectrophotometry using TLC or HPLC analysis based on the absorbance change caused by the conversion. Using this method, the actinomycete strain A8 was isolated as a cyclic dipeptide-producing strain. The cyclic dipeptides were purified from the microbial extract by enzymatic detection-guided fractionation, and their structures were determined to be cyclo(L-Phe-L-Pro) and cyclo(L-Pro-L-Tyr) by spectroscopic methods.

Actinobacteria↗
PubMed2006

A highly sensitive and multiplexed method for focused transcript analysis.

We describe a novel, multiplexed method for focused transcript analysis of tens to hundreds of genes. In this method TRAC (transcript analysis with aid of affinity capture) mRNA targets, a set of amplifiable detection probes of distinct sizes and biotinylated oligo(dT) capture probe are hybridized in solution. The formed sandwich hybrids are collected on magnetic streptavidin-coated microparticles and washed. The hybridized probes are eluted, optionally amplified by a PCR using a universal primer pair and detected with laser-induced fluorescence and capillary electrophoresis. The probes were designed by using a computer program developed for the purpose. The TRAC method was adapted to 96-well format by utilizing an automated magnetic particle processor. Here we demonstrate a simultaneous analysis of 18 Saccharomyces cerevisiae transcripts from two experimental conditions and show a comparison with a qPCR system. The sensitivity of the method is significantly increased by the PCR amplification of the hybridized and eluted probes. Our data demonstrate a bias-free use of at least 16 cycles of PCR amplification to increase probe signal, allowing transcript analysis from 2.5 ng of the total mRNA sample. The method is fast and simple and avoids cDNA conversion. These qualifications make it a potential, new means for routine analysis and a complementing method for microarrays and high density chips.

Amino Acid Sequence↗
PubMed2004

Improved method of analysis of biomass sugars using high-performance liquid chromatography.

The precise quantitative analysis of biomass derived sugars is a very important step in the conversion of biomass feedstocks to fuels and chemicals. However, the most accurate method of biomass sugar analysis is based on the gas chromatography analysis of derivatized sugars either as alditol acetates or trimethylsilanes. The derivatization method is time-consuming but the alternative HPLC method cannot resolve most sugars found in biomass hydrolysates. We have demonstrated for the first time that by careful manipulation of the HPLC mobile phase, biomass monomeric sugars (arabinose, xylose, fructose, glucose, mannose, and galactose) can be analyzed quantitatively and there is excellent baseline resolution of all the sugars. This was demonstrated for both standard sugars and corn stover hydrolysates. Our method can also be used to analyze dimmeric sugars (cellobiose and sucrose).

Biomass↗
PubMed1997

On the relation of mands and the function of destructive behavior.

When standard analogue functional analysis procedures produce inconclusive results in children with conversational speech, the child's mands may help to identify the function of destructive behavior. In the current investigation, functional analyses conducted with 2 children who exhibited self-injury, aggression, and property destruction were undifferentiated across conditions. Based on informal observations and school and parental report, an analysis was conducted using mands to help determine the function of the destructive behavior. Using a multielement design, the therapist's compliance with the child's mands occurred either on a fixed-ratio (FR) 1 schedule or contingent on destructive behavior. Destructive behavior occurred at high and consistent levels when reinforcement of mands was contingent on destructive behavior and at near-zero levels when reinforcement of mands occurred on the FR 1 schedule. Based on these results, a second analysis was conducted in which compliance to mands occurred only when the child appropriately requested it (i.e., functional communication training plus extinction) and, for 1 child, compliance with mands was terminated contingent upon destructive behavior (i.e., functional communication training plus response cost). For both children, the rates of destructive behavior decreased markedly. The results suggest that assessing the child's mands may be useful in decreasing destructive behavior when a functional analysis is inconclusive.

Adolescent↗
PubMed1988

Three spontaneous H-2Db mutants are generated by genetic micro-recombination (gene conversion) events. Impact on the H-2-restricted immune responsiveness.

Sequence analysis of the mutant Dbm13, Dbm14, and Dbm24 genes indicate that they differ from the parental Db gene by 4, 1, and 8 nucleotides, respectively. The mutant sequences substituted into Dbm13 and Dbm24 are identical to those found in the Kb gene, at the homologous positions. Thus, similar to the Kb gene, the Db gene is able to undergo micro-recombination (gene conversion) events with other class I genes. Such data suggest that micro-recombination events could be an important mechanism for the diversification of all H-2 genes. The Db mutant products share a common theme: the alterations in all occur at amino acid residues whose side chains in the homologous class I HLA-A2 molecule project into the postulated peptide antigen-binding cleft, and hence, would be expected to alter the binding of foreign or self peptides. Due to such changes, the bm14 mouse has become a nonresponder in the CTL response to Moloney murine leukemia virus (M-MuLV), as the alteration of one amino acid residue at position 70 (a Gln to His) is sufficient to entirely abrogate the cell-mediated response to the virus. On the other hand, the bm13 mouse has shifted the major part of its M-MuLV restriction to Kb, a profound alteration in CTL responsiveness due to the alteration of three amino acids (Leu to Gln at 114, Phe to Tyr at 116, and Glu to Asp at 119) in a peptide stretch of beta-pleated sheet structure lining the bottom of the antigen-binding cleft. Thus, study of these mutants reveals that, in one step, micro-recombination at the genetic level has resulted at the protein level in profound changes in the immune response to viral infection. Such a mechanism operating at the population level can be a driving force during evolution for modulating the character of CTL immunity.

Amino Acid Sequence↗
PubMed2004

Coordinate-based versus structural approaches to brain image analysis.

A basic issue in neurosciences is to look for possible relationships between brain architecture and cognitive models. The lack of architectural information in magnetic resonance images, however, has led the neuroimaging community to develop brain mapping strategies based on various coordinate systems without accurate architectural content. Therefore, the relationships between architectural and functional brain organizations are difficult to study when analyzing neuroimaging experiments. This paper advocates that the design of new brain image analysis methods inspired by the structural strategies often used in computer vision may provide better ways to address these relationships. The key point underlying this new framework is the conversion of the raw images into structural representations before analysis. These representations are made up of data-driven elementary features like activated clusters, cortical folds or fiber bundles. Two classes of methods are introduced. Inference of structural models via matching across a set of individuals is described first. This inference problem is illustrated by the group analysis of functional statistical parametric maps (SPMs). Then, the matching of new individual data with a priori known structural models is described, using the recognition of the cortical sulci as a prototypical example.

Brain↗
PubMed2000

Effect of the intensity of wireless telephone conversations on reaction time in a braking response.

Recently, concern has grown about the extent to which wireless telephone use by motor vehicle drivers constitutes a threat to traffic safety. This experiment investigated the effect of the intensity of wireless telephone conversations on reaction time (RT) for a braking response. Using a laboratory station to mimic the foot activity in driving, 16 adults were instructed to release the accelerator pedal and depress the brake pedal as quickly as possible following the activation of a red brake light. Mean RT was measured for 5 conditions which manipulated the intensity of a conversation, i.e., demand for attention, conducted on a wireless telephone. Analysis indicated that wireless telephone use caused a decrement in RT, however, there was no significant effect associated with intensity of the conversation across intensity.

Accidents, Traffic↗
PubMed1999

Changing cyclosporin A formulation: an analysis in paediatric cardiac transplant recipients.

Cyclosporin A is the primary immunosuppressive agent used in cardiac transplantation to maintain chronic immunosuppression. Absorption may be erratic and major side-effects include nephrotoxicity. A recently introduced formulation (Neoral) improves absorption in cystic fibrosis heart-lung transplant recipients, but episodes of rejection have been reported on conversion from the oil-based formulation. A retrospective analysis of 21 paediatric cardiac transplant recipients who had been converted from the oil-based formulation to the micro-emulsified formulation was performed. No clinical rejection episodes occurred following conversion. There was a significant reduction in dose following conversion (p < 0.001). The mean trough level was less on the new formulation (p = 0.04), but there was no difference in coefficient of variation or standard deviation. Mean glomerular filtration rate (GFR) was significantly less, but there was no difference in the rate of change of GFR on the new formulation. Erratic absorption and deteriorating renal function remain as significant problems in paediatric cardiac transplant recipients despite conversion to the new formulation.

Adolescent↗
PubMed1981

Relation between the efficiency of homothallic switching of yeast mating type genes and the distribution of cell types.

Homothallic switching of yeast mating type genes occurs as often as each cell division, so that a colony derived from a single haploid spore soon contains an equal number of MATa and MAT alpha cells. Cells of opposite mating types conjugate, and eventually the colony contains only nonmating MATa/MAT alpha diploids. Mutations that reduce the efficiency of homothallic MAT conversions yield colonies that still contain many haploid cells of the original spore mating type plus a few recently generated cells of the opposite mating type. These (a greater than alpha)- or (alpha greater than a)-mating colonies also contain some nonmating diploid cells. As an alternative to microscopic pedigree analysis to determine the frequency of mating type conversions in a variety of mutant homothallic strains, we analyzed the proportions of MATa, MAT alpha, and MATa/MAT alpha cells in a colony by examining the mating phenotypes of subclones. We developed a mathematical model that described the proportion of cell types in a slow-switching colony. This model predicted that the proportion of nonmating cells would continually increase with the size (age) of a colony derived from a single cell. This prediction was confirmed by determining the proportion of cell types in colonies of an HO swi1 strain that was grown for different numbers of cell divisions. Data from subcloning (a greater than alpha) and (alpha greater than a) colonies from a variety of slow-switching mutations and chromosomal rearrangements were used to calculate the frequency of MAT conversions in these strains.

Alleles↗
PubMed2005

Recovering haplotype structure through recombination and gene conversion.

MOTIVATION: Understanding haplotype evolution subject to mutation, recombination and gene conversion is fundamental to understand genetic specificities of human populations and hereditary bases of complex disorders. The goal of this project is to develop new algorithmic tools assisting the reconstruction of historical relationships between haplotypes and the inference of haplotypes from genotypes. RESULTS: We present two new algorithms. The first one finds an optimal pathway of mutations, recombinations and gene conversions leading to a given haplotype of size m from a population of h haplotypes. It runs in time O(mhs(2)), where s is the maximum number of contiguous sites that can be exchanged in a single gene conversion. The second one finds an optimal pathway of mutations and recombinations leading to a given genotype, and runs in time O(mh(2)). Both algorithms are based on a penalty score model and use a dynamic programming approach. We apply the second one to the problem of inferring haplotypes from genotypes, and show how it can be used as an independent tool, or to improve the performance of existing methods. AVAILABILITY: The algorithms have been implemented in JAVA and are available on request.

Algorithms↗