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At least 199 records · Page 11Linked to original sources
PubMed1989

Organization of ribosomal RNA genes in Alternaria alternata Japanese pear pathotype, a host-selective AK-toxin-producing fungus.

DNA encoding ribosomal RNA (rRNA) of Alternaria alternata Japanese pear pathotype has been cloned in lambda replacement vector, lambda Fix. Restriction endonuclease mapping and Southern hybridization with the 18S and 28S rRNAs of Saccharomyces cerevisiae revealed the A. alternata rDNA to be tandemly repeating 8.15-kilobase pair unit. The restriction fragments of the unit were then subcloned in the plasmid vector Bluescribe M13- and partially sequenced. The determined sequences were compared with previously reported sequences of S. cerevisiae rRNAs and their genes. The locations of DNA sequences encoding the 5.8S, 18S, and 28S rRNAs were determined by homology search using reported sequences. The complete DNA sequence for 5.8S rRNA of the fungus was found to be highly conserved at more than 90% homology in the fungi analyzed. However, sequence diversities were observed in limited regions involved in a helix structure, the helix (e), found at position 116-137.

Alternaria↗
PubMed1988

Developmental changes in composition and quality of prickly pear cactus cladodes (nopalitos).

The composition and quality of edible tender stems or cladodes of 3 Prickly Pear Cactus species (Opuntia amyclaea, O. ficus-indica, and O. inermis) were studied at different stages of development. This traditional Mexican vegetable is called "nopalitos" in Spanish and "cactus leaves" in English. Cladodes harvested when 20 cm in length have the following average composition per 100 g: 91.7 g of water, 1.1 g of protein, 0.2 g of lipid, 1.3 g of ash, 1.1 g of crude fiber, 4.6 g of complex carbohydrates and 0.82 g of simple sugars, 12.7 mg of ascorbic acid and 28.9 micrograms of carotenes. The cladode's juice has an average pH of 4.6, 0.45% titratable acidity and 6.9% soluble solids. The components which varied most during development of the cladodes were: carotenes, acidity and total carbohydrates which increased, and protein and crude fiber (acid-detergent) which decreased. The nutritive value of the tender cladodes in the stages of growth at which they are commonly harvested and consumed (15 to 25 cm long weighing 50 to 80 g per stem), was similar for the 3 species.

Ascorbic Acid↗
PubMed1977

[Determination of patulin in foodstuffs Part II: Determination of patulin in tomatoes, pears, apples cucumbers and plums (author's transl)].

An analytical method for the determination of Patulin in tomatoes, pears, apples, cucumbers and plums is described. The determination limit of the method is 40 mug Patulin/kg. With additions between 100-500 mug Patulin/kg the recovery rates lie between 86--95%. After a pre-purification of the crude extract by column chromatography and liquid-liquid extraction the Patulin is determined thin-layer chromatographically by reflectance measurement at 273 nm.

Fruit↗
PubMed1997

Isoxaben soil biodegradation in pear tree orchard after repeated high dose application.

During the past nine years, each of the plots of a pear tree orchard were treated annually with the same herbicide treatment. The following herbicide treatments were compared, each being made by application of a mixture of two or three herbicides: 1a, no herbicide at all, weeds being hoed (control 1a); 2, diuron + paraquat 3 + 1 kg/ha; 3, simazine + paraquat 2 + 1 kg/ha; 4, isoxaben + diuron + paraquat 0.5 + 1.6 + 1 kg/ha; and 5, isoxaben + simazine + paraquat 0.5 + 1.25 + 1 kg/ha. In March 1996, one year after the final orchard herbicide treatment, isoxaben could not be detected in the soils of any field plots; isoxaben was incorporated at 0.74 mg/kg in the loamy soils sampled separately in each of the field plots, and the soils were incubated in the laboratory. Isoxaben soil half-lives were 92 days in the soils treated previously with herbicide treatments 1a, 2, or 3 and 42 days in the soils treated with herbicide treatments 4 and 5. The repeated isoxaben treatments applied in the past thus enhanced the isoxaben soil biodegradation; diuron, simazine, and paraquat had no influence on this rate enhancement. On the other hand, herbicide treatments 4 and 5 were applied in the orchard in April 1996 on the corresponding plots treated in this manner for the last nine years. Isoxaben + paraquat 0.5 + 1 kg/ha was applied simultaneously on other plots (control 1b) not treated in the past with isoxaben. During the growth season in the orchard, the isoxaben soil half-lives in the control plots 1b was 101 days, and 41 days in the plots where herbicide treatments 4 or 5 were applied.

Benzamides↗
PubMed2004

Expression of viral EPS-depolymerase reduces fire blight susceptibility in transgenic pear.

Erwinia amylovora is the causal agent of fire blight of Maloideae. One of the main pathogenicity factors of this bacterium is the exopolysaccharide (EPS) of its capsule. In this paper, we used genetic transformation tools to constitutively express an EPS-depolymerase transgene in the pear (Pyrus communis L.) cv. Passe Crassane with the aim of decreasing its high susceptibility to fire blight. Expression of the depolymerase gene in 15 independent transgenic clones led, on average, to low depolymerase activity, although relatively high expression was observed at the transcriptional and translational levels. Only two of the transgenic clones (9X and 10M) consistently showed a decrease in fire blight susceptibility in vitro and in the greenhouse. These clones were also among the highest expressers of depolymerase at the RNA and enzyme activity levels. The correlation observed among all transgenic clones between depolymerase expression and fire blight resistance suggested the potential of this strategy.

Bacterial Capsules↗
PubMed2006

In vitro regeneration of wild pear (Pyrus pyraster Burgsd) clones tolerant to Fe-chlorosis and somaclonal variation analysis by RAPD markers.

An in vitro adventitious regeneration system under selective pressure was established in Pyrus pyraster Burgsd to obtain somaclones with higher adaptability to calcareous soils. P. pyraster is important species, both for its relative closeness to cultivated pear and for reforestation of marginal farmland and for the production of timber. Shoot regeneration was induced from leaves and vegetative apices of in vitro-grown shoots on a modified LP medium supplemented with naphtaleneacetic acid (1.07 microM) and benziladenine (BA, 8.9 microM). After 30 days, explants were transferred to an expression medium consisting of the same basal medium with only BA present. Selective treatments utilized MS medium with Fe-EDTA replaced by equimolar amount of FeSO4 with either KHCO(3) or NaHCO(3). Through the selection process 11 putatively tolerant lines were obtained from vegetative shoot apices. RAPD analysis was performed on these lines to allow comparison to the mother clone. A total of seven 10-mer primers were used to amplify all the genotypes and 74 scorable fragments were produced. These were analysed using the Dice similarity index, showing genetic variability among the 11 regenerated clones and between them and the mother clone.

Adaptation, Physiological↗
PubMed1998

Style-specific and developmentally regulated accumulation of a glycosylated thaumatin/PR5-like protein in Japanese pear (Pyrus serotina Rehd.).

The stylar proteins of Japanese pear (Pyrus serotina Rehd.) were analyzed by two-dimensional gel electrophoresis, and a 32-kDa protein with an isoelectric point of 4.8 was found to be a major component in the style. The 32-kDa protein was a soluble glycoprotein which reacted with concanavalin A. The 32-kDa protein specifically accumulated in the style in a developmentally regulated manner, but was not detected in the other floral organs and leaves. An oligonucleotide representing the N-terminal amino acid sequence of the 32-kDa protein was used to amplify a cDNA fragment by polymerase chain reaction (PCR). The generated PCR product was used to screen a style cDNA library. The selected cDNA clone encoded 244 amino acid residues containing the N-terminal sequence of the 32-kDa protein. The N-terminus of the protein was preceded by putative signal peptide of 22 amino acid residues. The 32-kDa protein showed significant homology with the thaumatin/PR5-like proteins, and was named PsTL1 (Pyrus serotina thaumatin-like protein 1). The possible biological role of PsTL1 in the styles is discussed.

Amino Acid Sequence↗
PubMed2003

Instability of short-sequence DNA repeats of pear pathogenic Erwinia strains from Japan and Erwinia amylovora fruit tree and raspberry strains.

An array of short-sequence DNA repeats (SSRs) occurs in the plasmid pEA29 of the fire blight pathogen Erwinia amylovora. A large number of "fruit tree" strains, mainly from Central and Western Europe, were screened for their SSR numbers, and the analyses were extended to five raspberry strains from North America and six pear pathogenic Erwinia strains from Japan. The repeat ATTACAGA present in all E. amylovorastrains was found to be reiterated 3 to 15 times. The Japanese strains contained the major repeat sequence GGATTCTG, which was reiterated 16 to 24 times. ATTACAGG, which resembles the SSR of E. amylovora, was reiterated two or three times. In a novel approach, sequencing gels were used to visualize the rare occurrence of shorter arrays (down to three repeats) in E. amylovoraand the Japanese Erwinia strains. Changes in the repeat numbers in E. amylovora were observed repeatedly when the bacteria had been exposed to stress conditions. The repeat structures of homo- and heteroduplices of PCR-amplified repeats were also analyzed by cleavage of annealed molecules with the single-strand-specific endonuclease from bacteriophage T4. Not only heteroduplexes, but also homoduplexes showed non-matching regions in the SSRs, which could arise from transient formation of loops due to strand slippage during the assays.

Base Sequence↗
PubMed2005

Biochemical and nutritional characterization of three prickly pear species with different ripening behavior.

Biochemical and nutritional changes were studied during the ripening process of three Opuntia morphospecies with different ripening behavior: Naranjona (O. ficus-indica), Blanca Cristalina (Opuntia sp.), and Esmeralda (Opuntia sp.) of early, early-intermediate, and intermediate-late ripening, respectively. In loss of fresh weight, Naranjona showed the highest values, while in Blanca Cristalina and Esmeralda, a discrete weight loss was found. No significant differences were found among morphospecies in soluble solids, total titratable acidity and pH during the postharvest days. Blanca Cristalina and Esmeralda showed an increase in the content of carotenoids, while these diminished in Naranjona. The cell wall enzymes evaluated showed particular behaviors during the ripening of each morphospecies suggesting a fine biochemical control and not a clear relationship between fruit softening and enzyme activity. This study provides basic information on prickly pear ripening, in order to understand this process for its control and for improving shelf life.

Area Under Curve↗
PubMed1979

Computed tomographic evaluation of pear-shaped bladder.

Computed tomography (CT) was used to distinguish between pelvic lipomatosis and idiopathic inferior vena caval thrombosis as a cause of a pear-shaped bladder seen on intravenous urography. The findings on CT were explicit in explaining the patient's clinical problem.

Adult↗
PubMed2005

Stable maintenance and expression of a foreign gene in transgenic pear shoots retrieved from in vitro conservation.

Shoot-tips of transgenic pear were successfully conserved in vitro by slow-growth and cryopreservation methods. After 1 year of storage in slow growth conditions, all shoot-tips survived showing shoot re-growth. Similarly, shoot-tips showed high survival and regeneration rates after cryopreservation. The genetic stability of the transgenic GUS construct in shoots recovered from slow-growth and cryopreservation was assessed. The results from polymerase chain reaction and Southern blotting showed the stable maintenance of the GUS gene in genome, and the Single-Strand Conformation Polymorphism assay did not detect single base variation. X-Gluc staining suggested a normal expression of the GUS gene in shoots retrieved from these storage methods.

Blotting, Southern↗
PubMed2002

Isolation and structure of D-xylans from pericarp seeds of Opuntia ficus-indica prickly pear fruits.

Xylans were isolated from the pericarp of prickly pear seeds of Opuntia ficus-indica (OFI) by alkaline extraction, fractionated by precipitation and purified. Six fractions were obtained and characterized by sugar analysis and NMR spectroscopy. They were assumed to be (4-O-methyl-D-glucurono)-D-xylans, with 4-O-alpha-D-glucopyranosyluronic acid groups linked at C-2 of a (1-->4)-beta-D-xylan. The sugar composition and the 1H and 13C NMR spectra showed that their chemical structures were very similar, but with different proportions of D-Xyl and 4-O-Me-D-GlcA. Our results showed that, on average, the water soluble xylans have one nonreducing terminal residue of 4-O-methyl-D-glucuronic acid for every 11 to 14 xylose units, whereas in the water non-soluble xylans, xylose units can varied from 18 to 65 residues for one nonreducing terminal residue of 4-O-methyl-D-glucuronic acid.

Magnetic Resonance Spectroscopy↗
PubMed2001

Application of high-performance liquid chromatography to the characterization of the betalain pigments in prickly pear fruits.

The qualitative and quantitative betalain pigment content of two cultivars of prickly pear (Opuntia ficus-indica) fruits grown in southeastern Spain was evaluated. After methanolic extraction of crushed fruits, reversed-phase high-performance liquid chromatography and photodiode array detection were applied simultaneously for the separation, identification and quantification of these pigments. Two main pigments were obtained, which were identified as indicaxanthin (lambda(max) 484 nm) and betanin (lambda(max) 535 nm). Spectrophotometric evaluation of both pigments showed a yield of around 20-30 mg per 100 g of fresh pulp. When the influence of temperature (25 to 90 degrees C) on betacyanin pigment stability was investigated, the results revealed a substantial degree of thermodegradation at temperatures higher than 70 degrees C.

Betalains↗
PubMed2001

Simple ion chromatographic method for the determination of chlormequat residues in pears.

Current methods for quantitative determination of chlormequat residues in food crops are characterized by rather low recoveries and the need for derivatization (in case of gas chromatography, GC), or by high capital investment (in case of liquid chromatography-mass spectrometry, LC-MS). We propose a cation-exchange chromatography method for the analysis of chlormequat in pears. The method is based on extraction of the target compound with 40 mM HCl, followed by centrifugation and filtration. The filtrate is directly injected into an ion chromatograph equipped with a commercially available cation-exchange column and a suppressed conductivity detection system. While the limit of detection (LOD) (0.5 mg/kg) may not be small enough to allow dietary analysis, the method meets all validation requirements and is an alternative for the existing GC and LC-MS methods in quality control.

Chlormequat↗
PubMed2002

Determination of chlormequat and mepiquat in pear, tomato, and wheat flour using on-line solid-phase extraction (Prospekt) coupled with liquid chromatography-electrospray ionization tandem mass spectrometry.

A sensitive and selective method is presented for the simultaneous analysis of the pesticides chlormequat and mepiquat at trace levels in tomato, pear, and wheat flour. The method entails direct injection of the food extract onto an on-line solid-phase extraction (SPE) instrument (Prospekt) using a strong cation-exchange resin. Analyte separation and detection is done by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS). Surrogate standards (d9-chlormequat, d6-mepiquat) are employed to compensate for recovery losses and potential MS-MS signal suppression. The method achieves a limit of quantification for both cationic analytes at or below 5 microg/kg, and good intra- and inter-assay precision with mean variability values <7% over a concentration range up to 195 microg/kg. This study also addresses potential analyte carry-over in an SPE on-line system, as well as the robustness of the procedure and its applicability in routine quality control operations.

Calibration↗
PubMed1998

Multiresidue determination of pesticides in apples and pears by gas chromatography-mass spectrometry.

This paper describes a rapid, specific and sensitive multiresidue method for the routine analysis of several classes of pesticides used for the treatment of apples and pears, involving a rapid extraction procedure at pH 4.5 with a mixture of acetone-dichloromethane-hexane (50:20:30, v/v/v) and gas chromatography coupled to mass-selective detection, in order to achieve quantitative analysis down to their respective maximum residue limit. Extraction recoveries were between 55 and 98%. Limits of detection and limits of quantitation ranged respectively, from 0.01 to 0.05 mg/kg and from 0.02 to 0.1 mg/kg. Intra-assay relative standard deviation was less than 19% for all compounds. An excellent linearity was observed from these LOQs up to 500 mg/kg. Intermediate (inter-assay) precision and accuracy were satisfactory. The method has been applied to many fruit samples intended for commercialisation.

Fruit↗
PubMed1999

Liquid chromatography-electrospray mass spectrometry multi-residue determination of pesticides in apples and pears.

This paper describes a rapid, specific and sensitive multi-residue method for the routine quantitative analysis of pesticides of several classes used for the treatment of apples and pears, down to their respective maximum residue limits (MRLs). It involves a rapid extraction procedure and liquid chromatography coupled to electrospray mass selective detection. Seven pesticides were extracted at pH 4.5 with a mixture of acetone-dichloromethane-hexane (50:20:30, v/v/v). Ionization was performed at atmospheric pressure in an electrospray-type source and detection was carried out using the selected ion monitoring (SIM) mode. Extraction recoveries were between 55 and 98% except for methylthiophanate (< 20%). Limits of detection (LODs) and limits of quantitation (LOQs) ranged, respectively, from 0.01 to 0.02 mg/kg and from 0.02 to 0.05 mg/kg, with relative standard deviation (R.S.D.) less than 19%. An excellent linearity was observed for LOQs up to 5 mg/kg. Intermediate ("inter-assay") precision and accuracy were satisfactory. The method was applied to many fruit samples intended for commercialization.

Chromatography, High Pressure Liquid↗
PubMed1999

Fast separation of (poly)phenolic compounds from apples and pears by high-performance liquid chromatography with diode-array detection.

Polyphenolic compounds in apples and pears were analysed by HPLC on C18-modified silica. Gradient elution with phosphoric acid-methanol mixtures and phosphoric acid-acetonitrile mixtures gave complete separation of all polyphenolics of interest. The use of methanol as modifier was preferred because it provides a more rapid separation (20 min). Diode-array detection was used for the provisional identification of polyphenolic compounds not available as standards.

Acetonitriles↗