Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pear”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources
PubMed1980

Cell Wall Metabolism in Ripening Fruit: II. CHANGES IN CARBOHYDRATE-DEGRADING ENZYMES IN RIPENING ;BARTLETT' PEARS.

Mature ;Bartlett' pear (Pyrus communis) fruits were ripened at 20 C. Fruits at different stages of ripeness were homogenized, and extracts of the low speed pellet (crude cell wall) were prepared. These extracts contained polygalacturonase, pectin esterase, and activity against seven p-nitrophenyl glycoside substrates. Polygalacturonase, alpha-galactosidase, and alpha-mannosidase increased in activity as the fruit ripened. Cellulase and activities against pear wall xylan and arabinan were absent from the extracts.

Journal Article↗
PubMed1982

Polyribosomes from Pear Fruit: II. CHANGES OCCURRING IN PULP TISSUES DURING RIPENING AND SENESCENCE.

Detailed analyses of polysome profiles from lyophilized pulp tissues of pear fruits (Pyrus communis L. cv. Passe-Crassane) at different stages of ripening and senescence, and estimates of the amount of polysomal-associated mRNA, lead to the conclusions that during senescence (ripening), the ripening and the over-ripening processes can clearly be separated and respectively linked to the first and the second increase in the large mRNA species. Ethylene synthesis which occurs at the beginning of a normal ripening at 15 degrees C after a cold storage or an ethephon treatment is related to an increase in mRNA and ribosomal material found only in pulp tissues. Finally, we suggest that in the pear fruit, the sequence of events which occurs during senescence (ripening) is initiated by two systems which regulate ethylene biogenesis, and that the first system is efficient only at low temperatures (from 0 to 4 degrees C).

Journal Article↗
PubMed1983

Ethylene production by auxin-deprived, suspension-cultured pear fruit cells in response to auxins, stress, or precursor.

Auxin-deprived, mannitol-supplemented, suspension-cultured pear (Pyrus communis L. Passe Crassane) fruit cells produce large quantities (20-40 nanoliters ethylene per 10(6) cells per hour) of ethylene in response to auxins, CuCl(2) or 1-amino-cyclopropane-1-carboxylic acid (ACC). Maximum rates of production are achieved about 12 hours after the addition of optimal amounts of indoleacetic acid (IAA), naphthalene acetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 4 to 5 hours after the addition of CuCl(2) and 1 to 2 hours after the addition of ACC. Supraoptimal concentrations of IAA result in a lag phase followed by a normal response. High concentrations of NAA and 2,4-D result in an early (4-5 hours) stress response and injury.Continuous protein and RNA synthesis are essential for elaboration of the full IAA response; only protein synthesis is necessary for the response to CuCl(2) and ACC. Based on polysomal states and rates of amino acid incorporation, CuCl(2) partially inhibits protein synthesis while nonetheless stimulating ethylene production. In general, ethylene production by the pear cells resembles that of other plant systems. Some differences may reflect the sensitivity of the cells and are discussed. The relatively high levels of ethylene produced and the experimental convenience of the cultured cells should make them especially suitable for further investigations of ethylene production and physiology.

Journal Article↗
PubMed1985

Ethylene production by suspension-cultured pear fruit cells as related to their senescence.

Suspension-cultured pear fruit cells produce low levels of ethylene during growth and division in auxin containing medium. When deprived of auxin, division gradually ceases and ethylene production falls to barely discernible levels. However, notable ethylene production can now be induced by indoleacetic acid, CuCl(2), or 1-aminocyclopropane-1-carboxylic acid. If the auxin-deprived cells are transferred to ;aging' medium that lacks auxin but contains 0.4 molar mannitol, inducible ethylene production increases several-fold reaching levels of 40 to 60 nanoliters/10(6) cells per hour. Maximum inducible ethylene productivity is attained at varying times (1-6 days) after transfer to aging medium and appears to be temporally related to cell survival, i.e. the time of subsequent cell death. It is argued that auxin depletion initiates senescence which, in turn, leads to a transient increase in inducible ethylene production and eventual death. The limitations and potentials of the suspension-cultured pear cells as a system for the study of cellular senescence are discussed.

Journal Article↗
PubMed1986

The induction of ethylene production from pear cell culture by cell wall fragments.

Macerase, a pectinase-containing enzyme mixture, was used to digest cell walls isolated from cultured pear cells. Following digestion, the reaction mixture was boiled to inactivate enzymes. Addition of soluble aliquots of the mixture to suspension cultures of pear cells led to a rapid and transient production of ethylene by the cells.

Journal Article↗
PubMed1987

Inhibition of pear fruit ripening by mannose.

Softening of the flesh and the rise in ethylene evolution and respiration associated with ripening in pear (Pyrus communis L.) fruit was delayed when mannose was vacuum infiltrated into intact fruit. The extent of delay could be modified by altering the concentration or the volume of mannose applied to the fruit. Inhibition of ripening was associated with phosphorylation of mannose to mannose 6-phosphate (M6P), and accumulation of M6P was associated with lowered levels of inorganic phosphate (Pi), glucose 6-phosphate (G6P), and ATP in the fruit tissue. Subsequently, however, as the M6P was metabolized, the levels of Pi, G6P, and ATP increased and ripening processes were concomitantly released from inhibition. Hence, the degree of inhibition by mannose or the release from inhibition was related to the level of M6P in the fruit and its rate of metabolism. The data provide correlative evidence to support a view that one inhibitory effect of mannose is depletion of Pi in the cell as a result of phosphorylation of mannose to M6P. Inhibition of ripening by mannose was not alleviated by co-application of glucose as a competitive substrate for the hexokinase(s), or by Pi, presumably the depleted metabolite. Also, incubation of tissue disks with M6P resulted in inhibition of ethylene production and respiration. The structural analogs of mannose, glucosamine, and 2-deoxyglucose, which have been shown to mimic mannose action in several plant tissues, did not cause inhibition of ripening of pear fruit comparable with that associated with mannose. Both analogs stimulated respiration, and glucosamine caused only a small inhibition of softening and ethylene evolution. Another mannose analog, alpha-methylmannoside, did inhibit fruit ripening though to a lesser extent than mannose. Its influence was also associated with accumulation of M6P and a decrease of Pi levels. We conclude that the mannose effect may, in part, be due to M6P toxicity, as well as by depletion of Pi.

Journal Article↗
PubMed1991

Ethylene production by growing and senescing pear fruit cell suspensions in response to gibberellin.

A pear (Pyrus communis L. cv Passe Crassane) cell suspension was used as a model system to study the influence of gibberellin on processes related to fruit ripening. Growth of the cell cultures was inhibited and their loss of viability was accelerated when 0.5 millimolar gibberllic acid (GA(3)) was added to suspensions at two stages of cell development, namely, growth and quiescence. Cell respiration rate was unaffected up to 2 millimolar GA(3) but ethylene production, both basal and 1-aminocyclopropane-1-carboxylic acid-induced, was inhibited at all stages of cell development. However, the degree of inhibition decreased as the cell cultures aged. The site of ethylene inhibition by GA(3) appeared to be related to the ethylene-forming enzyme. The coincident acceleration of cell senescence and inhibition of ethylene production indicate that the pear cell suspension cannot serve as an analogous model for studying the mode of action of gibberellin in delaying ripening and senescence of fruits in its entirety, although certain specific effects might be relevant.

Journal Article↗
PubMed1991

Induction and regulation of ethylene biosynthesis by pectic oligomers in cultured pear cells.

Pectic oligomers induced a rapid, transient increase in ethylene biosynthesis when added to pear cells in suspension culture. The rate of ethylene biosynthesis increased within 30 to 40 minutes after oligomer addition, reached a maximum between 90 and 120 minutes after addition, and then decreased to basal rates of synthesis. Both the rapid increase and decrease in biosynthesis appear to be precisely regulated components of the ethylene response to oligomers. Induction of ethylene biosynthesis by pectic oligomers resulted in a reduced sensitivity of cells to further ethylene induction. This reduction in sensitivity occurred within 90 minutes after an oligomer treatment, slightly preceding the decline in ethylene synthesis. The degree of insensitivity induced was proportional to the concentration of oligomer in the first treatment. Induced insensitivity to elicitors appears to represent a novel mechanism which may limit continued ethylene biosynthesis after ethylene induction. Ethylene was produced by pear cells throughout the cell growth cycle, as cells increased in density over a 6 day period. Endogenous ethylene biosynthesis was at a maximum during the first 4 days of rapid cell growth, then declined to half the peak rate through day 10. Pectic oligomers could induce an increase in ethylene biosynthesis above this background rate only after day 5, as endogenous biosynthesis declined. Changes in sensitivity to added oligomer during the growth cycle may result from insensitivity to elicitors induced by growth processes.

Journal Article↗
PubMed1993

Uterine and placental alterations in pregnant sows associated with the porcine epidemic abortion and respiratory syndrome (PEARS).

In the winter of 1990/91 a new, economically devastating disease occurred in european pig breeding herds, characterized by late-term abortion, stillbirth and a high morbidity and mortality of suckling piglets. Because of the clinical picture the disease was named porcine epidemic and respiratory syndrome (PEARS). In this study investigations were carried out in tissues of uterus and placentae of late gestational sows (107 to 112 days of gestation) in three different groups of animals: group I = control animals (n = 2) group II = naturally infected sows (n = 12) from farms, where PEARS recently had been introduced; group III = sows (n = 2), experimentally inoculated with placental homogenates from animals of group II. Both in naturally infected as well as in experimentally infected sows a multifocal, lymphohistiocytic vasculitis and perivascular cell infiltration was observed in the endometrium and maternal part of the placenta, but not in the fetal one. In the fetomaternal unit there were multifocal microseparations of the epithelial layers present. Transmission electron microscopically spherical or oval virus-like particles of 45 to 75 mm in diameter were frequently found on the surface of endothelial cells of blood vessels in the maternal placenta, in a few cases in the intercellular channel system between uterine epithelial cells or on endothelial cells of capillaries in the fetal placenta. Serological results indicate, that an infection with Lelystad virus had occurred in naturally and experimentally infected sows and that transplacental infection was present.

Abortion, Veterinary↗
PubMed2004

Molecular differentiation of Erwinia amylovora strains from North America and of two Asian pear pathogens by analyses of PFGE patterns and hrpN genes.

In order to determine a possible genomic divergence of Erwinia amylovora'fruit tree' and raspberry strains from North America, several isolates were differentiated by pulsed-field gel electrophoresis (PFGE) analysis, the size of short DNA sequence repeats (SSRs) and the nucleotide and deduced amino acid sequences of their hrpN genes. By PFGE analysis European strains are highly related, whereas strains from North America were diverse and were further distinguished by the SSR numbers from plasmid pEA29. The E. amylovora strains from Europe showed identical HrpN sequences in contrast to the American isolates from fruit trees and raspberry. Those were related to each other, but distinguishable by their HrpN patterns. The Asian pear pathogens differed in HrpN among each other and from E. amylovora. Erwinia pyrifoliae isolates and the Erwinia strains from Japan were ordered via their HrpN sequences in agreement with the PFGE patterns. For all three pathogens, dendrograms from PFGE and sequence data indicate an evolutionary diversity within the species in spite of a genetic conservation for parts of the hrpN genes suggesting a long persistence of the Asian pear pathogens in Korea and Japan as well as of fire blight in North America. Some of the divergent American E. amylovora isolates share PFGE patterns with the relatively uniform European strains.

Amino Acid Sequence↗
PubMed1989

Pearly penile papules: treatment with the carbon dioxide laser.

Pearly penile papules are frequently occurring lesions located over the corona and sulcus of the penis. They are asymptomatic and are considered to be acral angiofibromas. Some individuals, disturbed by their presence, request removal of the lesions. Even after patients are assured of the benign nature of the process and its relatively high incidence, prominent lesional involvement may still cause significant psychological distress. Two patients with pearly penile papules have been successfully treated with the carbon dioxide laser. A review of the literature and description of treated cases are presented.

Carbon Dioxide↗
PubMed2000

Binding affinity of the methyl ester of AK-toxin I to membrane fractions from Japanese pear leaves.

The binding site of AK-toxin, a host-specific toxin against Japanese pear, was searched for in the membrane fractions of the pear leaves, using 3H-labeled AK-toxin I methyl ester. Binding activity, which was displaceable by the unlabeled ligand, was observed for microsomal fraction from a toxin-susceptible cultivar, Nijisseiki. However, the binding was also observed for those from toxin-resistant cultivars, Kosui and Hosui. Detection of the specific binding failed for the plasma membrane fraction which was prepared from microsomal fraction of the toxin-susceptible cultivar by aqueous two-phase separation, and the hitherto presumed model of the AK-toxin receptor in the plasma membrane could not be verified.

Binding, Competitive↗
PubMed2004

[Effects of zinc and boron nutrition on balsam pear (Momordica charantia) yield and quality, and polyamines, hormone, and senescence of its leaves].

Field trial and physiological determination on the effects of zinc and boron nutrition on balsam pear (Momordica charantia) yield and quality and on polyamines, hormone, and senescence of its leaves showed that application of ZnSO4.7H2O and Na2B4o7.10H2O on Zn and B deficient soils could increase balsam pear yield and its contents of protein, Vc and 17 sorts of amino acids, especially the contents of essential amino acids for human body, but decrease the NO3(-)-N content. The reason was that Zn and B could increase polyamines (PAs), putrescine (Put), spermidine (Spd), spermine (Spm), indole acetic acid (IAA), gibberellic acid (GA3) and ascorbic acid (ASA) contents and superoxide dismutase (SOD), peroxidase (POD) and catalase(CAT) activities, and reduce malondialdehyde (MDA), abscisic acid (ABA) contents in leaves, which inhibited membrane lipid peroxidation. The results also showed that there was a significant positive correlation between yields and PAs, Put, Spd, Spm, GA3, SOD, POD, CAT, but a significant negative correlation with MDA and ABA contents in leaves. There was a significant positive correlation between MDA and ABA, but a significant negative correlation with PAs, Put, Spd, Spm, IAA, GA3, ASA, SOD, POD, and CAT.

Aging↗
PubMed2004

[Relationship between breaking of dormancy and reactive oxygen species metabolism in flower buds of pear].

The metabolism of reactive oxygen species in pear (Pyrus bretschneideri Rehd.) flower buds changes greatly during their natural dormancy in winter. The O(-.)(2) production rate increases rapidly during the period of dormancy, but decreases when dormancy finishes (Fig. 5). H(2)O(2) content goes up significantly at the early stage of dormancy, but afterwards falls gradually (Fig. 5). However, ascorbic acid (AsA) and reduced glutathione (GSH) contents show a different changing trend: descending at first and keeping at relatively low levels during the process of dormancy, but rising during breaking of dormancy (Fig. 4). The activities of superoxide dismutase (SOD), ascorbic peroxidase (APX) and glutathione reductase (GR) descend during the process of dormancy, but rise during breaking of dormancy, although at different rates for different enzymes (Figs. 1, 3). On the contrary, the activity of catalase (CAT) increases sharply at the beginning of dormancy, keeps at a stable high level during dormancy, and gradually decreases at the end of dormancy period (Fig. 2). The activity of peroxidase (POD) even keeps increasing during dormancy and breaking of dormancy (Fig. 1). The results show that the metabolism of reactive oxygen species has certain strong correlation with the natural dormancy of pear flower buds in winter.

Ascorbic Acid↗
PubMed2005

Postharvest heat and cold treatment to control Ceratitis capitata on cactus pear fruit.

In order to work out a quarantine treatment for cactus pear fruit a factorial experimental plan was carried combining postharvest water dips at 20, 50, 54, 58 and 60 degrees C and storage at 1 degrees C for 3, 6 and 10 days. Cactus pear fruit cv 'Rossa' were artificially infested with Med. fly eggs (at least 20 eggs per fruit) then left in the lab at 25 degrees C for 4 days. Treatments took place by dipping the fruit at each water temperature for 2 mm. At each established time fruit was picked and checked for vital larvae and degree of chilling injury (CI). Probit 9 requirements were achieved in all cases when fruit was cold-stored for 10 days. When fruit was kept for 6 days the quarantine requirement was achieved only by dipping the fruit at 58 and 60 degrees C while none dip treatment was effective if fruit was stored for 3 days at 1 degrees C. All Fruit stored for 10 days at 1 degrees C showed severe CI symptoms and when kept for 6 days the same degree of CI was found on fruit dipped in water at 20, 58 and 60 degrees C. No CI was observed after 3 days at 1 degrees C. In conclusion only when fruit was dipped at 50-54 degrees C and stored for 10 days at 1 degrees C the probit 9 condition was attained with acceptable CI symptoms.

Animals↗
PubMed1978

Intracranial pearly tumors: the roles of computed tomography, angiography, and pneumoencephalography.

The findings is computed tomography (CT) and other radiological examinations in nine histologically proven cases of intracranial pearly tumors are presented. The CT findings include a low density lesion with no enhancement after contrast medium injection and in some cases a lesser degree of mass effect than would be expected from the size and site of such lesions. Pneumoencephalography is superior to CT in detecting suprasellar pearly tumors when they are isodense with the cerebrospinal fluid.

Adult↗
PubMed2025

The genome sequence of the Pearly Heath, Coenonympha arcania Linnaeus, 1761 (Lepidoptera: Nymphalidae).

We present a genome assembly from a female specimen of Coenonympha arcania (Pearly Heath; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The assembly contains two haplotypes with total lengths of 480.99 megabases and 458.33 megabases. Most of haplotype 1 (99.95%) is scaffolded into 29 chromosomal pseudomolecules, including the Z sex chromosome. Haplotype 2 was assembled to scaffold level. The mitochondrial genome has also been assembled, with a length of 15.28 kilobases.

Coenonympha arcania↗
PubMed2000

Effect of pH and temperature on the thermostability of prickly pear (Opuntia ficus-indica) yellow-orange pigments.

The colour stability of the yellow-orange pigment (lambda max = 476 nm) of prickly pear (Opuntia ficus-indica) fruit was determined as a function of temperature and pH. The experiments were carried out at three different temperatures (50, 70 and 90 degrees C) with pigment solutions at pH values ranging from 2-7. The degree of pigment retention decreased with increasing temperature as a function of increasing thermal exposure time with least pigment degradation at pH 5. The reaction rate constants were determined as 0.0062, 0.0383 and 0.1102 min-1 for a thermal degradation reaction rate of pseudo-first order. The activation energy was calculated as 65.1 kJ.mol-1.

Color↗