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At least 1,009 records · Page 56Linked to original sources
PubMed1999

Effect of gene conversion on polymorphic patterns at major histocompatibility complex loci.

The pattern of polymorphisms at MHC loci was studied by computer simulations and by DNA sequence analyses, with special reference to synonymous and non-synonymous divergence among alleles. A model of overdominance plus short-term selection was simulated for a gene family with allelic and non-allelic gene conversion. It was found that the ratio of non-synonymous-to-synonymous divergence among alleles decreases as the non-allelic conversion becomes more frequent. On the other hand, the ratio of synonymous divergence at the antigen recognition site to that at non-coding region increases by non-allelic conversion. By comparing such a pattern with the observed values of mammalian genes, it is suggested that non-allelic conversion is less frequent in human genes than in genes of other mammals. A quantitative analysis on the patchwork pattern was attempted by using identity excess among nucleotide sites of a gene. Comparison of simulation results with DNA data analysis shows that the rate of allelic conversion is high.

Animals↗
PubMed1999

Isotope ratio monitoring gas chromatography/Mass spectrometry of D/H by high temperature conversion isotope ratio mass spectrometry.

Of all the elements, hydrogen has the largest naturally occurring variations in the ratio of its stable isotopes (D/H). It is for this reason that there has been a strong desire to add hydrogen to the list of elements amenable to isotope ratio monitoring gas chromatography/mass spectrometry (irm-GC/MS). In irm-GC/MS the sample is entrained in helium as the carrier gas, which is also ionized and separated in the isotope ratio mass spectrometer (IRMS). Because of the low abundance of deuterium in nature, precise and accurate on-line monitoring of D/H ratios with an IRMS requires that low energy helium ions be kept out of the m/z 3 collector, which requires the use of an energy filter. A clean mass 3 (HD(+.)) signal which is independent of a large helium load in the electron impact ion source is essential in order to reach the sensitivity required for D/H analysis of capillary GC peaks. A new IRMS system, the DELTA(plus)XL(trade mark), has been designed for high precision, high accuracy measurements of transient signals of hydrogen gas. It incorporates a retardation lens integrated into the m/z 3 Faraday cup collector. Following GC separation, the hydrogen bound in organic compounds must be quantitatively converted into H(2) gas prior to analysis in the IRMS. Quantitative conversion is achieved by high temperature conversion (TC) at temperatures >1400 degrees C. Measurements of D/H ratios of individual organic compounds in complicated natural mixtures can now be made to a precision of 2 per thousand (delta notation) or, better, with typical sample amounts of approximately 200 ng per compound. Initial applications have focused on compounds of interest to petroleum research (biomarkers and natural gas components), food and flavor control (vanillin and ethanol), and metabolic studies (fatty acids and steroids). Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1998

Identification of novel temperature-sensitive lethal alleles in essential beta-tubulin and nonessential alpha 2-tubulin genes as fission yeast polarity mutants.

We have screened for temperature-sensitive (ts) fission yeast mutants with altered polarity (alp1-15). Genetic analysis indicates that alp2 is allelic to atb2 (one of two alpha-tubulin genes) and alp12 to nda3 (the single beta-tubulin gene). atb2(+) is nonessential, and the ts atb2 mutations we have isolated are dominant as expected. We sequenced two alleles of ts atb2 and one allele of ts nda3. In the ts atb2 mutants, the mutated residues (G246D and C356Y) are found at the longitudinal interface between alpha/beta-heterodimers, whereas in ts nda3 the mutated residue (Y422H) is situated in the domain located on the outer surface of the microtubule. The ts nda3 mutant is highly sensitive to altered gene dosage of atb2(+); overexpression of atb2(+) lowers the restrictive temperature, and, conversely, deletion rescues ts. Phenotypic analysis shows that contrary to undergoing mitotic arrest with high viability via the spindle assembly checkpoint as expected, ts nda3 mutants execute cytokinesis and septation and lose viability. Therefore, it appears that the ts nda3 mutant becomes temperature lethal because of irreversible progression through the cell cycle in the absence of activating the spindle assembly checkpoint pathway.

Alleles↗
PubMed1998

Pharmacoeconomic analysis of using Sinemet CR over standard Sinemet in parkinsonian patients with motor fluctuations.

OBJECTIVE: To compare the costs of pharmacotherapy in patients with Parkinson's disease before and after converting from standard Sinemet to extended-release Sinemet CR. DESIGN: Investigators retrospectively reviewed records of patients converting from Sinemet to Sinemet CR for efficacy and total drug costs. Cost-effectiveness was evaluated retrospectively from data collected in prospective Sinemet CR efficacy trials. SETTING: Parkinson's disease clinic at a tertiary care university teaching hospital. PATIENTS: 100 patients with motor fluctuations who had undergone an initial 6-month course of Sinemet therapy, followed by a 6-month course of Sinemet CR. MAIN OUTCOME MEASURES: Total cost was measured as the cost of Sinemet formulations plus the costs of other antiparkinson medications. Differences in pre- and postconversion costs were compared by using the paired, two-tailed Student's t-test. A substudy of 39 patients on the cost-effectiveness of conversion measured the ratio of daily medication costs to the daily hours "on" without chorea. RESULTS: While total daily medication costs after conversion increased by 21%, patients experienced either a comparable or an improved degree of disease control with Sinemet CR. Patients who were also taking selegiline were able to decrease selegiline expense by 20%. The costs of other adjunctive medications did not differ significantly after conversion. The cost-effectiveness analysis revealed an increase in postconversion on time by 2.2 hours (p = 0.0001), accompanied by a $2.85 decrease in total cost per hour on without chorea (p = 0.11). CONCLUSIONS: Although Sinemet CR is more costly, it may be more cost-effective in patients with motor fluctuations. Some patients may be able to reduce adjunctive medications.

Adult↗
PubMed2000

[Causes of unsuccessful attempts of laparoscopic cholecystectomy].

Based on an analysis of personal observations and literature data the authors made an analysis of the frequency and causes of unsuccessful laparoscopic cholecystectomy (LChE) resulting in laparotomy (conversion). LChE was successful in 217 of 233 operations. In 16 patients (6.9%) conversion was performed. According to the summary data of the literature on 150,000 cases of LChE the frequency of conversion was from 0.9 to 18%. The frequency of conversions was found to depend on the strategy of determining the indications for LChE and on the level of technological maintenance of operations. Three groups of the causes of conversion were set up on the basis of an analysis of publications about 498 cases of unsuccessful attempts of LChE and 16 personal observations: pathomorphological (393--78.9%; 7--43.8%); iatrogenic (99--19.9%; 7--43.8%) and technico-instrumental (6--1.2%; 2--12.4%). The pathomorphological causes lead to noncomplicated conversion and indicate to the limited use of LChE for the concrete patients. The iatrogenic and technico-instrumental causes appear all of a sudden and require emergent laparotomy. So the total frequency of conversion can not be a criterion for the assessment of complications after LChE. It is expedient to make a special analysis of the causes of transition to laparotomy and to distinguish the complicated and not complicated conversion.

Adolescent↗
PubMed1978

The conversion of aryl sulfate ester salts to alkyl aryl derivatives suitable for analysis by electron impact mass spectrometry.

A series of monosubstituted (CH3, CH3O, Cl Br or NO2 at the O, m and p position) phenyl sulfate ester salts were derivatized to form n-propyl aryl sulfate diesters. The derivatization was accomplished by reacting aryl sulfate ester salts, AgClO4 and n-propyl iodide in SO2 at--40 degree C. The mass spectra of all the n-propyl aryl sulfate esters showed an intense molecular ion and intense diagnostic peaks at M--42 ([aryl--OSO3H]+) and M--122 ([ARYL--OH]+). The utility of this procedure for derivatizing selected sulfate ester conjugated xenobiotics and steroids was demonstrated.

Arylsulfonates↗
PubMed2006

Analysis of a processing system for proteases using yeast cell surface engineering: conversion of precursor of proteinase A to active proteinase A.

The display of a protease, carboxypeptidase Y (CPY) or procarboxypeptidase Y (proCPY), which is the vacuolar protease, on the yeast-cell surface was successfully performed using yeast-cell-surface engineering for the first time. Through that we could confirm the processing of vacuolar proteases containing proteinase A (PrA) and proteinase B (PrB) which are related to the maturation of proCPY, using a novel cell-surface engineering technique. Various protease-knockout strains of Saccharomyces cerevisiae with the CPY-displaying system were constructed to evaluate the operation of the activation process of CPY. The display of CPY (CPY-agg, which is a fusion protein of CPY with C-terminal half of alpha-agglutinin) on the cell surface was confirmed by immunofluorescence staining. The activity of the CPY-agg was determined after the conversion of proCPY to active CPY by treatment of whole cells with proteinase K. In the proCPY-displaying CPY-knockout strain and PrB-knockout strain, CPY was displayed as an active (mature) form, but in the proCPY-displaying PrA-knockout strain, CPY was present as an inactive form (proCPY). These facts indicate that PrA had been already activated before its transport to the vacuole and that active mature PrA might convert proCPY to CPY before the transport of proCPY to the vacuole. From these results, it was suggested that by using the yeast-cell-surface engineering at the location of the initial step, the autocatalytic activation from proPrA to PrA might occur before the vacuolar branch separates from the main secretory pathway.

Antigens, Surface↗
PubMed2003

Optimization of lipase-catalyzed biodiesel by response surface methodology.

Biodiesel prepared by catalyzed mild transesterification has become of much current interest for bioenergy. The ability of a commercial immobilized lipase (Novo Industries--Bagsvaerd, Denmark) from Rhizomucor miehei (Lipozyme IM-77) to catalyze the transesterification of soybean oil and methanol was investigated in this study. Response surface methodology and 5-level-5-factor central composite rotatable design were employed to evaluate the effects on reaction time, temperature, enzyme amount, molar ratio of methanol to soybean oil, and added water content on percentage weight conversion to soybean oil methyl ester by transesterification. Based on ridge max analysis, the optimum synthesis conditions giving 92.2% weight conversion were: reaction time 6.3 h, temperature 36.5 degrees C, enzyme amount 0.9 BAUN (Batch Acidolysis Units NOVO), substrate molar ratio 3.4:1, and added water 5.8%.

Bioelectric Energy Sources↗
PubMed1995

Use of computer-assisted image analysis for noninvasive evaluation of oral lichenoid reactions and oral leukoplakia.

The objective of the present study was to elaborate and to evaluate a method in which the clinical appearance of a mucosal lesion could be expressed by means of color and morphologic features extracted from digitized images. The ability to express mucosal changes with image features was evaluated, as was the accuracy of a classification of the lesions on the basis of image feature analysis. Computer-assisted image analysis was performed on digitized color slides from 76 patients with lichenoid reactions that included both oral lichen planus and contact lesions and 20 patients with homogenous oral leukoplakia. Color features were measured according to the intensity-hue-saturation color system, and morphologic features were estimated by tracing the hyperkeratotic area. Hyperkeratinizing and inflammatory tissue reactions could be demonstrated and defined by image analysis. Image features indicating inflammatory tissue reactions were more pronounced in cases of oral lichenoid reactions. Morphologic parameters could express the anatomic appearance of the lesions. The comparison between histopathologic diagnosis and a classification through computerized analysis demonstrated that 90.5% of oral lichenoid reactions could be separated from homogenous oral leukoplakia by linear discriminant analysis.

Analog-Digital Conversion↗
PubMed2002

Rapid purification and analysis of alpha-synuclein proteins: C-terminal truncation promotes the conversion of alpha-synuclein into a protease-sensitive form in Escherichia coli.

Parkinson's disease (PD) is the most common neurodegenerative movement disorder and is characterized by the loss of dopaminergic neurons and the formation of eosinophilic intracytoplasmic inclusion bodies known as Lewy bodies. Although alpha-synuclein is known to be a pivotal factor implicated in the pathogenesis of PD, its function remains to be elucidated. We used the pGEX expression system to develop a simple and rapid method for purifying alpha-synuclein proteins in suitable forms for biochemical studies of their functions. The wild-type alpha-synuclein protein was overexpressed in Escherichia coli and purified to approx. 80% purity with relatively high yields. We also used this expression system to investigate the expression pattern of the various domains of alpha-synuclein. With the exception of the alpha-synuclein protein that was truncated at amino acid residue 95, all domain constructs of alpha-synuclein were purified at similar levels with relatively high yields. Unexpectedly, removal of amino acid residues 96-140 in the C-terminal acidic region of alpha-synuclein promotes its conversion to a protease-sensitive form during expression and purification in E. coli. Our study suggests a method for generating useful reagents to investigate the molecular mechanism by which alpha-synuclein regulates the pathogenesis of PD.

Escherichia coli↗
PubMed2001

High frequency mitotic gene conversion in genetic hybrids of the oomycete Phytophthora sojae.

Microbial populations depend on genetic variation to respond to novel environmental challenges. Plant pathogens are notorious for their ability to overcome pesticides and host resistance genes as a result of genetic changes. We report here that in particular hybrid strains of Phytophthora sojae, an oomycete pathogen of soybean, high frequency mitotic gene conversion rapidly converts heterozygous loci to homozygosity, resulting in heterokaryons containing highly diverse populations of diploid nuclei. In hybrids involving strain P7076, conversion rates of up to 3 x 10(-2) per locus per nucleus per generation were observed. In other hybrids, rates were of the order of 5 x 10(-5). Independent gene conversion was observed within a selected linkage group including loci as close as 0.7 kb apart and in unlinked markers throughout the genome. Gene conversions continued throughout vegetative growth and were stimulated by further sexual reproduction. At many loci, conversion showed extreme disparity, with one allele always being lost, suggesting that conversion was initiated by allele-specific double-stranded breaks. Pedigree analysis indicated that individual loci undergo multiple independent conversions within the nuclei of a vegetative clone and that conversion may be preceded by a heritable "activation" state.

Alleles↗
PubMed1999

Conversion of 3-chlorocatechol by various catechol 2,3-dioxygenases and sequence analysis of the chlorocatechol dioxygenase region of Pseudomonas putida GJ31.

Pseudomonas putida GJ31 contains an unusual catechol 2,3-dioxygenase that converts 3-chlorocatechol and 3-methylcatechol, which enables the organism to use both chloroaromatics and methylaromatics for growth. A 3.1-kb region of genomic DNA of strain GJ31 containing the gene for this chlorocatechol 2,3-dioxygenase (cbzE) was cloned and sequenced. The cbzE gene appeared to be plasmid localized and was found in a region that also harbors genes encoding a transposase, a ferredoxin that was homologous to XylT, an open reading frame with similarity to a protein of a meta-cleavage pathway with unknown function, and a 2-hydroxymuconic semialdehyde dehydrogenase. CbzE was most similar to catechol 2,3-dioxygenases of the 2.C subfamily of type 1 extradiol dioxygenases (L. D. Eltis and J. T. Bolin, J. Bacteriol. 178:5930-5937, 1996). The substrate range and turnover capacity with 3-chlorocatechol were determined for CbzE and four related catechol 2,3-dioxygenases. The results showed that CbzE was the only enzyme that could productively convert 3-chlorocatechol. Besides, CbzE was less susceptible to inactivation by methylated catechols. Hybrid enzymes that were made of CzbE and the catechol 2, 3-dioxygenase of P. putida UCC2 (TdnC) showed that the resistance of CbzE to suicide inactivation and its substrate specificity were mainly determined by the C-terminal region of the protein.

Amino Acid Sequence↗