Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pollen development”

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 901 records · Page 50Linked to original sources
PubMed1998

Comparison of inflammatory events in skin sites with and without cutaneous late-phase reactions after prominent immediate IgE-mediated responses.

BACKGROUND: A number of inflammatory events have been detected in skin chambers overlying sites of developing late-phase reactions (LPR) to pollen antigens in sensitive subjects. However, the pathogenic significance of such events is still unclear. OBJECTIVE: We sought to compare inflammatory responses and cytokine levels in skin chambers that overlie sites of antigen challenge in individuals with and individuals without LPRs after immediate wheal responses of similar intensity. RESULTS: Early histamine releases at antigen sites were similar in eight subjects with LPR (+/+ group) and eight subjects without LPR (+/- group). However, histamine releases during hours 2 through 5 of antigen challenge were significantly greater in the +/+ subjects than in the +/- subjects. Total exuding leukocytes; percent eosinophils; and levels of eosinophil cationic protein, lactoferrin, and IL-8 were significantly greater at antigen versus buffer control challenge sites in both the +/+ and +/- groups, with no significant differences between the groups. IL-1 and IL-6 levels were not greater at antigen sites than at buffer sites. CONCLUSIONS: The only significantly greater antigen-induced response detected in +/+ subjects than in +/- subjects was in later histamine release, which is possibly a marker of other inflammatory responses because histamine itself does not induce LPRs. Other inflammatory events assessed may be somewhat greater in +/+ subjects, but not significantly so.

Antigens↗
PubMed1999

The Arabidopsis thaliana dhdps gene encoding dihydrodipicolinate synthase, key enzyme of lysine biosynthesis, is expressed in a cell-specific manner.

Lysine synthesis in prokaryotes, some phycomycetes and higher plants starts with the condensation of L-aspartate-beta-semialdehyde (L-ASA) and pyruvate into dihydrodipicolinic acid. The enzyme that catalyses this step, dihydrodipicolinate synthase (DHDPS), is inhibited by the end-product lysine and is therefore thought to have a regulatory control on lysine synthesis. We have cloned and sequenced an Arabidopsis thaliana DNA fragment containing 900 bases upstream of the dhdps coding sequence. A transcriptional fusion of this fragment with the beta-glucuronidase reporter gene (uidA. Gus) was used to study the transcription properties of this promoter fragment (DS). No lysine-induced repression on transcription could be detected. Expression of DS-Gus activity in transformed Arabidopsis thaliana and Nicotiana tabacum was found to be cell type-specific. In the vegetative parts of the plant, GUS activity was located in meristems and young vasculature of roots, in vasculature of stem and leaves and in the meristems of young shoots. In flowers, high expression was found in the carpels, style, stigma, developing embryos, tapetum of young anthers and pollen. We demonstrated that the Arabidopsis DS promoter can direct its cell type-specific expression in a heterologous plant, Nicotiana tuabacum. The importance of transcriptional regulation of the dhdps gene, and in more general genes involved in amino acid biosynthesis, is discussed.

Amino Acid Sequence↗
PubMed1989

Mating system in rye: variability in relation to the population and plant density.

The amount of outcrossing was estimated using seven enzyme loci assayed in seven populations of rye (Secale cereale L.). Single-locus outcrossing values fluctuated widely from locus to locus in each population. The weighted mean single-locus estimates ranged from 0.716 to 0.946, and multilocus estimates ranged from 0.701 to 0.910. The analysis showed that self-pollination occurred in the rye populations, and, as a result of selfing, populations contained homozygotes in excess of random mating expectations at the seedling stage of development. Low plant density, which causes low pollen density during fertilization, seems to weaken the self-incompatibility system; at low plant density, the outcrossing estimate was significantly lower than was obtained at high plant density.

Breeding↗
PubMed2004

Vaccination with genetically engineered allergens prevents progression of allergic disease.

IgE-mediated allergy affects >25% of the population in industrialized countries. Repeated contact with the disease-eliciting allergens induces rises of allergen-specific IgE Abs and progression of the disease to more severe manifestations. Our study uses a type of vaccine that is based on genetically modified allergen derivatives to treat allergic patients. We developed hypoallergenic derivatives of the major birch pollen allergen, Bet v 1, by genetic engineering and vaccinated birch pollen-allergic patients (n = 124) in a double-blind, placebo-controlled study. Active treatment induced protective IgG Abs that inhibited allergen-induced release of inflammatory mediators. We also observed a reduction of cutaneous sensitivity as well as an improvement of symptoms in actively treated patients. Most important, rises of allergen-specific IgE induced by seasonal birch pollen exposure were significantly reduced in vaccinated patients. Vaccination with genetically engineered allergen derivatives is a therapy for allergy that not only ameliorates allergic reactions but also reduces the IgE production underlying the disease.

Allergens↗
PubMedDate not supplied

Airborne (1-->3)-beta-D-glucan and airway disease in a day-care center before and after renovation.

Changes in symptoms and airway responsiveness among persons who worked in a day-care center that had microbial growth problems were assessed before and after renovation. Before and after the building renovation, the investigators used the Limulus assay with (1-->3)-beta-D-glucan-specific lysate to measure airborne levels of (1-->3)-beta-D-glucan, a cell-wall component of molds. Airway responsiveness and subjective symptoms were measured among 14 female employees with a methacholine test and a standardized questionnaire. After the renovation, (1-->3)-beta-D-glucan-glucan levels decreased from 11.4 to 1.4 ng/m3. The number of persons who had increased airway responsiveness decreased after the renovation. Two employees developed a classical allergy to cat and pollen during the observation period. Although the study included only a few subjects and was based on only one day-care center, the data suggest that (1-->3)-beta-D-glucan may be related to airways inflammation caused by indoor air pollution.

Adult↗
PubMed2004

Evolution by reticulation: European dogroses originated by multiple hybridization across the genus rosa.

The European dogroses (Rosa sect. Caninae (DC.) Ser.) are characterized by a unique meiosis system ("canina-meiosis"), which controls the heterogamous development of tetraploid egg cells and haploid pollen grains resulting in a pentaploid somatic status. This permanent anorthoploidy is supposed to have originated by a hybridization event in the postglacial period. In this study we present molecular evidence by an analysis of nuclear ribosomal DNA data that dogroses are complex allopolyploids resulting from multiple hybridization events. As previously described, the nrITS-1 region does not undergo concerted evolution in dogroses. Thus, different ITS-1 sequences persist within single individuals. Secondary structure predictions do not point to the existence of pseudogenes within these ITS-1 types. Our data suggest that the pentaploid Caninae genome originated from different members of nondogroses and the now extinct Protocaninae.

Biological Evolution↗
PubMed1979

Developmental expression of genetically defined peptidases in maize.

The activities of genetically defined amino- and endopeptidases of maize were compared in pericarp, endosperm, and embryonic tissue of the maize kernel from 5 days postpollination until harvest. Activities were highest in the immature stages and declined as drying progressed. The expression of some of the peptidase genes contributed by the pollen parent was examined during early endosperm development in an F(1) cross. The paternally contributed peptidase variants could first be detected 7 days after pollination.During germination and early seedling growth the peptidase activities continued to decline in the endosperm but maintained high levels in the scutellum. The maize peptidases probably have no direct role in hydrolysis of endosperm storage proteins during germination and growth.The peptidase isozymes were associated with the soluble cytoplasmic fraction of the maize scutellum during early growth. Only one tissue specificity was found for the peptidases. Occurrence of a particular aminopeptidase isozyme, AMP2, is limited to endosperm tissue during kernel maturation.

Journal Article↗
PubMed1992

Changes in the cellular profile of induced sputum after allergen-induced asthmatic responses.

Allergen inhalation causes airway inflammation and an increase in histamine airway responsiveness. We have used cell counts in sputum induced by hypertonic saline aerosol to assess airway inflammation before and 32 h after asthmatic responses to allergen. Twelve asthmatic subjects (mean age, 27.4 yr; range, 20-38 yr) had an inhalation test with D. farinae, ragweed pollen, or cat extract. All of them developed an early response with a fall in FEV1, of 24.8% (SD, 6.3%); nine of 12 had a definite late response (fall in FEV1 greater than or equal to 15%), and 10 of 12 had an increase in airway responsiveness to histamine at 32 h (PC20 reduced by greater than twofold). Sputum was induced by hypertonic saline after the histamine test, before and 32 h after the allergen challenge, at the same time of day. The quality of the sample was scored according to visual inspection and inverted microscopy and by salivary contamination. Plugs arising from the lower respiratory tract were selected for further evaluation. Differential cell counts of eosinophils (Eo) and metachromatic cells (MCC) (mast cell and basophils) were obtained from direct smears, blind to the clinical procedures. The mean fall in FEV1 after hypertonic saline was 6.4% (range, zero to 28%). The sputum samples were adequate in 79.5% of attempts. Eo and MCC increased significantly from 3.8 (4.4) to 18.2 (22.8)% (p = 0.01) and from 0.05 (0.17) to 0.25 (0.76)% (p = 0.04), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2006

Arabidopsis microRNA167 controls patterns of ARF6 and ARF8 expression, and regulates both female and male reproduction.

In flowering plants, diploid sporophytic tissues in ovules and anthers support meiosis and subsequent haploid gametophyte development. These analogous reproductive functions suggest that common mechanisms may regulate ovule and anther development. Two Arabidopsis Auxin Response Factors, ARF6 and ARF8, regulate gynoecium and stamen development in immature flowers. Wild-type pollen grew poorly in arf6 arf8 gynoecia, correlating with ARF6 and ARF8 expression in style and transmitting tract. ARF6 and ARF8 transcripts are cleavage targets of the microRNA miR167, and overexpressing miR167 mimicked arf6 arf8 phenotypes. Mutations in the miR167 target sites of ARF6 or ARF8 caused ectopic expression of these genes in domains of both ovules and anthers where miR167 was normally present. As a result, ovule integuments had arrested growth, and anthers grew abnormally and failed to release pollen. Thus, miR167 is essential for correct patterning of gene expression, and for fertility of both ovules and anthers. The essential patterning function of miR167 contrasts with cases from animals in which miRNAs reinforce or maintain transcriptionally established gene expression patterns.

Animals↗
PubMed1994

[Prevention of exposure in respiratory allergies].

Sensitization to indoor allergens like house-dust mite and animal dander as well as outdoor allergens like grass and tree pollen play an important role in the development to atopic airway disease, i.e. atopic rhinitis and conjunctivitis and allergic asthma. Studies on emergency room patients in the US showed that the sensitization to cat dander and house-dust mite Dermatophagoides represented risk factors for acute attacks of asthma. However, irrespective of the inheritance of atopy, disease of specific organs and expression of symptoms remain highly variable and are likely to depend on a multiplicity of environmental factors, the most important of which is likely to be the level of exposure to the sensitizing allergen. There is increasing evidence that exposure to potential allergens early in life is important. Concentrations and timing of the exposure seem fundamental. The elimination of allergens in households of atopic individuals is crucial in a prophylaxis and therapy. There have been several publications on mite allergen elimination procedures; a lot of them are uncontrolled, and allergen reduction is not significant. This article tries to compare trials reporting of improvement of clinical symptoms and significant reduction of indoor allergens with those trials which did not achieve significant results.

Allergens↗
PubMed1994

[Pollenosis in children in the Tatra Mountain region].

BACKGROUND: During the last 20 years we can observe a marked rise of allergic diseases in the child and adult population with a dominant increase of pollenoses in children. It is assumed that this adverse development is due to changes in the ecosystem caused above all by contamination of the living environment. Our objective was to examine school children in Tatranská Strba and Strbské Pleso as regards sensitization to different groups of pollen allergens. By investigating several factors associated with the development of the disease, the authors wanted to elucidate the prevalence of pollenosis in the environment devoid of industrial exhalations. METHODS AND RESULTS: The investigated group comprised 160 school children aged 6-15 years (mean age 10.4 years) incl. 83 boys (mean age 10.1 years) and 77 girls (mean age 10.7 years). Skin tests revealed sensitization to pollen allergens in 50 boys (60.2%) and 35 girls (45.5%). Positivity to grass pollen was found in 35.7%, to weeds and bushes in 16.3% and to pollen from trees in 7.8%. The percentage of positivity to individual types of pollen allergens as well as the maximum of clinical complaints corresponds to the type of vegetation where the children live. The influence of genetic factors was manifested at the 92% level of significance (p = 0.056), after Yates' correction (p = 0.081). Atopic children have in 62.4% a positive family-history. In conjunction with the incidence of allergoses the test of rank correlation confirmed statistically significant agreement between sick and healthy children as regards the period of breastfeeding (p = 0.0024), beginning of attendance of preschool facilities (p = 0.0052) as well as the month of birth (p = 0.0150). CONCLUSIONS: From the investigation ensues that the local vegetation has an impact on the specific sensitization of individual subjects and plays a part in the manifestation of pollenosis in a relatively clean environment--the High Tatras being considered such. It can be assumed that the coincidence of genetic factors, lifestyle and factors of the outdoor environment participate in the rising prevalence of pollenosis.

Adolescent↗
PubMed1992

Preferential expression of an alpha-tubulin gene of Arabidopsis in pollen.

The pool of tubulin protein in tissues of Arabidopsis is provided by the expression of multiple alpha-tubulin (TUA) and beta-tubulin genes. Whereas most tubulin genes are expressed in many tissues, previous evidence suggested that the TUA1 gene might be expressed primarily in pollen. We now report a detailed analysis of TUA1 expression during Arabidopsis development. In RNA from tissues of dissected flowers, TUA1 transcripts were detected only in stamens and mature pollen. Chimeric genes containing TUA1 5' flanking DNA fused to the beta-glucuronidase (GUS) coding region were used to create transgenic Arabidopsis plants. Plants containing a chimeric gene with 533 bp of 5' flanking sequence were analyzed by histochemical assay to localize GUS expression within the plant. The blue product of GUS enzyme activity accumulated very rapidly in postmitotic pollen grains. Much lower levels of GUS activity were detected in anthers with uninucleate pollen grains, in flower receptacles, and in a few vegetative tissues. Analysis of 5' deletions of the TUA1 promoter suggested that 97 bp of 5' flanking DNA is sufficient to drive GUS expression in pollen and young anthers, whereas at least 380 bp is required to detect GUS expression in the receptacle. Examination of the TUA1 promoter sequence revealed several motifs that are repeated within the TUA1 promoter and are similar to sequences in other pollen-specific promoters.

Base Sequence↗
PubMed2002

Immunocytochemical localization of allergenic proteins from mature to activated Zygophyllum fabago L. (Zygophyllaceae) pollen grains.

Zygophyllum fabago L. (Zygophyllaceae) can be found in the Middle East, in North Africa and in the arid zones of the Mediterranean region. It easily establishes itself in new regions, and is considered an invasive plant. They undergo ambophilous pollination, as there is a relationship between this type of pollination and its allergenic incidence. A combination of transmission electron microscopy with immunocytochemical methods was used to localize allergenic proteins during hydration and activation processes. Germination was induced in vitro for 1,2,4,6, and 30 min. The activated proteins reacting with antibodies present in human sera from allergenic patients are found in the cytoplasm, intine, exine and exudates from the pollen grains. The activation time plays an important role on the labelling intensity. Labelling of allergenic proteins was abundant at 1 and 2 min of activation, and decreased at 4 and 6 min. The rapid activation and release of the allergenic proteins appears to be the main cause of allergenic activity of Z. fabago pollen grains.

Allergens↗
PubMed1991

Isolation and developmental expression of Bcp1, an anther-specific cDNA clone in Brassica campestris.

Differential screening of a mature Brassica campestris pollen cDNA library has identified five cDNA clones that represent transcripts expressed exclusively, or at elevated levels, in pollen. We show here that the expression of one of these, clone Bcp1, is tissue specific and temporally regulated. The gene is activated during microspore development, as detected by in situ hybridization. Expression is enhanced at the time of pollen maturation and during pollen germination. In situ hybridization has also shown that Bcp 1 is activated in the tapetal cells in early anther development and continues to be expressed until tapetal dissolution. Homologous transcripts are present in pollen of other taxa of Brassicaceae including Arabidopsis, but not in pollen of any other families tested.

Amino Acid Sequence↗
PubMed2001

Evaluation of diets for the development and reproduction of Franklinothrips orizabensis (Thysanoptera: Aeolothripidae).

The suitability of ten diets for the development and reproduction of Franklinothrips orizabensis Johansen, the key natural enemy of Scirtothrips perseae Nakahara, a pest of California grown avocados, was determined in the laboratory. The experimental diets evaluated were: (i) irradiated Ephestia kuehniella Zeller eggs; (ii) irradiated E. kuehniella eggs and avocado pollen; (iii) Tetranychus pacificus McGregor eggs; (iv) T. pacificus eggs and avocado pollen; (v) irradiated E. kuehniella eggs and T. pacificus eggs; (vi) irradiated E. kuehniella eggs, T. pacificus eggs and avocado pollen; (vii) Scirtothrips perseae; (viii) Heliothrips haemorrhoidalis (Bouchè); (ix) avocado pollen; and (x) a young avocado leaf. Franklinothrips orizabensis larvae were unable to develop to adulthood on diets 9 and 10. The remaining eight diets supported complete development of F. orizabensis, but only diets 1, 2, 5, 6, 7 and 8 produced fecund females. On diet 5, F. orizabensis exhibited high larval to adult survivorship (90%), mated females exhibited highest daily and lifetime fecundity, and the progeny of mated females were female biased (53%). Analysis of jackknife estimates of net reproduction (Ro), intrinsic rate of increase (rm), and finite rate of increase (lambda) were all significantly greater for F. orizabensis reared on irradiated E. kuehniella eggs and T. pacificus eggs (i.e. diet 5) than corresponding values for other diets on which female F. orizabensis were able to complete development and reproduce. Incorporation of avocado pollen into diets had an adverse effect on demographic statistics for F. orizabensis, and low quality diets resulted in male biased sex ratios for this predator.

Animal Feed↗
PubMed2004

Nuclear SDH2-1 and SDH2-2 genes, encoding the iron-sulfur subunit of mitochondrial complex II in Arabidopsis, have distinct cell-specific expression patterns and promoter activities.

Three different nuclear genes encode the essential iron-sulfur subunit of mitochondrial complex II (succinate dehydrogenase) in Arabidopsis (Arabidopsis thaliana), raising interesting questions about their origin and function. To find clues about their role, we have undertaken a detailed analysis of their expression. Two genes (SDH2-1 and SDH2-2) that likely arose via a relatively recent duplication event are expressed in all organs from adult plants, whereas transcripts from the third gene (SDH2-3) were not detected. The tissue- and cell-specific expression of SDH2-1 and SDH2-2 was investigated by in situ hybridization. In flowers, both genes are regulated in a similar way. Enhanced expression was observed in floral meristems and sex organ primordia at early stages of development. As flowers develop, SDH2-1 and SDH2-2 transcripts accumulate in anthers, particularly in the tapetum, pollen mother cells, and microspores, in agreement with an essential role of mitochondria during anther development. Interestingly, in contrast to the situation in flowers, only SDH2-2 appears to be expressed at a significant level in root tips. Strong labeling was observed in all cell layers of the root meristematic zone, and a cell-specific pattern of expression was found with increasing distance from the root tip, as cells attain their differentiated state. Analysis of transgenic Arabidopsis plants carrying SDH2-1 and SDH2-2 promoters fused to the beta-glucuronidase reporter gene indicate that both promoters have similar activities in flowers, driving enhanced expression in anthers and/or pollen, and that only the SDH2-2 promoter is active in root tips. These beta-glucuronidase staining patterns parallel those obtained by in situ hybridization, suggesting transcriptional regulation of these genes. Progressive deletions of the promoters identified regions important for SDH2-1 expression in anthers and/or pollen and for SDH2-2 expression in anthers and/or pollen and root tips. Interestingly, regions driving enhanced expression in anthers are differently located in the two promoters.

Arabidopsis↗
PubMed2003

Prevention of allergen-specific IgE production and suppression of an established Th2-type response by immunization with DNA encoding hypoallergenic allergen derivatives of Bet v 1, the major birch-pollen allergen.

In atopic patients, programming towards a preferential Th2 immunity leads to IgE antibody production and cellular Th2 immunity against otherwise harmless antigens. We report the development of prophylactic and therapeutic DNA vaccines for the major birch-pollen allergen, Bet v 1. We constructed three DNA vaccines, coding for the complete cDNA, coding for two hypoallergenic fragments or coding for a hypoallergenic Bet v 1 mutant. The protective effect was studied in mice pretreated by intradermal DNA injections, then sensitized with Bet v 1 protein. Mice pretreated with any of the three Bet v 1-specific DNA vaccines were protected against allergic sensitization to Bet v 1. Protection was characterized by a lack of Bet v 1-specific IgE production, a lack of basophil activation and an enhanced IFN-gamma expression. DNA vaccines with wild-type Bet v 1 induced strong Bet v 1-specific antibody responses whereas DNA vaccines with hypoallergenic Bet v 1 derivatives induced no (fragments) or only transient (mutant) Bet v 1-specific antibody responses. A therapeutic approach with the fragment-DNA vaccine reduced IgE production and stimulated a sustained Th1 cytokine milieu. Our results demonstrate that DNA vaccines with hypoallergenic forms of the allergen specifically protect against sensitization and suppress established Th2-type responses. This concept may be applied for the development of safe and specific DNA vaccines for the prophylaxis and therapy of allergic diseases.

Allergens↗
PubMed1994

Mutagenic effects of heavy ion radiation in plants.

Genetic and developmental effects of heavy ions in maize and rice were investigated. Heavy particles with various charges and energies were accelerated at the BEVALAC. The frequency of occurrence of white-yellow stripes on leaves of plants developed from irradiated maize seeds increased linearly with dose, and high-LET heavy charged particles, e.g., neon, argon, and iron, were 2-12 times as effective as gamma rays in inducing this type of mutation. The effectiveness of high-LET heavy ion in (1) inhibiting rice seedling growth, (2) reducing plant fertility, (3) inducing chromosome aberration and micronuclei in root tip cells and pollen mother cells of the first generation plants developed from exposed seeds, and (4) inducing mutation in the second generation, were greater than that of low-LET gamma rays. All effects observed were dose-dependent; however, there appeared to be an optimal range of doses for inducing certain types of mutation, for example, for argon ions (400 MeV/u) at 90-100 Gy, several valuable mutant lines with favorable characters, such as semidwarf, early maturity and high yield ability, were obtained. Experimental results suggest that the potential application of heavy ions in crop improvement is promising. RFLP analysis of two semidwarf mutants induced by argon particles revealed that large DNA alterations might be involved in these mutants.

Argon↗