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P Creemers

Publications and source records attributed to P Creemers.

At least 19 recordsLinked to original sources
PubMed2005

Botrytis infection warnings in strawberry: reduced enhanced chemical control.

The fungal pathogen Botrytis cinerea is the causal agent of grey mould, the most important fungal fruit rot disease in strawberry in Europe. Currently disease control for grey mould is based on preventive spraying every five to seven days during flowering and harvest. Replacing preventive spraying with applications based on infection warnings can optimize performance and reduce the amount of sprays needed. Success of this approach will depend on the accuracy of the model used to predict disease outbreak. For this reason three infection models (BOTEM, BoWaS, DSS-Italy) were evaluated during the growth seasons of 2003 and 2004. The experiments included June bearing, retarded June bearing and ever bearing strawberries. In all experiments the use of infection models leaded to a reduced number of fungicide applications. However the efficacy of the different models towards the control of B. cinerea also decreased compared to the efficacy obtained with a standard 7 day schedule. Best results were obtained with BOTEM, developed by HRI (Horticultural Research International, East-Malling, UK): 17-60% reduction in fungicide use and an efficacy between 66-93 depending on the growth season, culture practice and the fungicides used. Compared with routine preventive spraying, the Botrytis fruit rot percentage is slightly higher. A higher efficacy with Botrytis infection warnings can only be obtained if infection warnings change from curative to preventive. A retroactive evaluation of a preventive warning system was included. Making use of the 48h weather forecasts supplied by the Royal Meteorological Institute of Belgium (KMI) based on ALADIN for the region of Haspengouw, it was possible to replace 30 up to 100% of the curative application by preventive spraying depending on the experiment and the threshold set for the preventive model.

Botrytis↗
PubMed2005

A new post-harvest fungicide to control fruit rot on apple and pear.

PHILABUSTER is a new post-harvest fungicide developed by Janssen Pharmaceutica N.V.. It provides an advanced mould control by post-harvest treatments of citrus and pome fruit. The product is formulated as a stable suspension concentrate intended for dilution in water before use. PHILABUSTER 400 SC contains 200 g/L imazalil and 200 g/L pyrimethanil. Both active ingredients have a different single site mode of action. Imazalil inhibits ergosterol biosynthesis (DMI), whereas pyrimethanil interferes with fungal enzyme secretion and methionine biosynthesis. Due to the combination of these low risk fungicides a good anti-resistance management can be obtained. In case of existing reduced sensitivity of a population to DMI or MBC fungicides, no cross-resistance with pyrimethanil was observed. PHILABUSTER showed good activity by post-harvest treatment against key pathogens on apple and pear Penicillium expansum (blue mold), Botrytis cinerea (gray mold) and Gloeosporium spp. (lenticel rot) in small and large scale experiments with artificial or natural infections. By dip treatment of large volumes of fruit (up to 50 tons) the depletion of both active ingredients in the treatment water was low, both when plastic or wooden bins were used. Lower dose rates resulted in an inferior and inconsistent residue level of both active ingredients on fruit. Possible advantages of post-harvest treatments versus field treatments for the control of storage diseases are discussed.

Botrytis↗
PubMed2004

Signum, a new fungicide with interesting properties in resistance management of fungal diseases in strawberries.

Signum, a new fungicide developed by BASF, was applied during 6 successive years against fungal diseases in strawberries. The product is formulated as a water dispersible granule, containing 6.7 % pyraclostrobin and 26.7 % boscalid. Pyraclostrobin is similar in chemistry to other strobilurin fungicides like kresoxim-methyl and trifloxystrobin, registered for fruit disease control. Boscalid belongs to the class of carboxyanilides. Both components in the premix formulation combine two different biochemical modes of action in the fungal cell respiration. Therefore, this co-formulation gives a broad-spectrum activity and also a reduced resistance risk for different target pathogens. Botrytis cinerea is the most important disease on strawberry-fruits and thus the control of fruit rot is mainly focused on this fungus. In average over 6 years, Signum has not only given a very good control against Botrytis fruit rot, but it has also shown a high performance in the control of Colletotrichum. Besides, Signum provides good control of powdery mildew (Podosphaera aphanis) and limits the shift to other fruit rots like leather rot (Phytophthora cactorum and leak (Rhizopus, Mucor). The availability of several categories of fungicide families with a different mode of action gives opportunities in alternating different fungicides and is the best guarantee for a sustainable control of fruit rot in all kinds of strawberry production methods. Signum should be integrated in an overall disease management program. Trials, in which the applications of Signum were timed on disease forecasting, based on environmental factors favorable for Botrytis development, were very promising. This tool can also help in establishing the IPM-concept in the production of strawberries.

Fragaria↗
PubMed1998

Rebound effect of the allogenic T-cell response to donor and third-party lymphocytes after cyclosporine withdrawal in renal transplant recipients.

Mixed lymphocyte reaction (MLR) assays were performed serially over 24 months in 19 first cadaver renal transplant recipients. Immunosuppression consisted of cyclosporine, methylprednisolone and azathioprine. Cyclosporine was withdrawn at 6 months postoperatively. The MLR reactivity gradually decreased over the first 3 months following transplantation. However, there was a significant increase in MLR reactivity at 12 months postoperatively after the cyclosporine withdrawal. This rebound effect in MLR reactivity following cyclosporine withdrawal could account for the increased incidence of acute rejection episodes.

Adult↗
PubMed1997

Sequential mixed lymphocyte culture after kidney transplantation: induction of tolerance or sensitization.

Serial mixed lymphocyte culture (MLC) was used to monitor the evolution of donor-specific responsiveness over the first 2 years after cadaveric renal transplantation. Lymphocytes obtained from 37 patients at 0, 1, 3, 6, 12, 18 and 24 months following transplantation were assayed in a one-way MLC using donor lymphocytes as stimulator cells. Donor-specific hyporesponsiveness developed in 66% of the patients with functioning grafts. Donor-specific sensitization was noted in 2 patients with functioning grafts and the MLC reactivity remained unchanged compared to the pretransplant value in 8 patients. The patients with donor-specific hyporeactivity tended to remain either free of rejection episodes or experienced early rejection episodes only. Thus, using serial MLC we were able to identify patients who developed hyporeactivity or tolerance to donor antigens. These patients may require less immunosuppression.

Adult↗
PubMed1997

Interaction between panel reactive antibodies, auto- and cold reactive antibodies, and a positive B cell cross-match in renal and cardiac allograft survival.

We analyzed the influence on allograft survival of pretransplant panel reactive antibodies (PRA) < 10%, PRA > 10%, autoantibodies, cold antibodies and a positive B cell crossmatch in 807 renal and 237 cardiac transplant recipients. Donors and recipients were predominantly of mixed ancestry (Khoi, San, Xhosa and Caucasoid). Log rank analysis showed that PRA < 10%, cold antibodies, and a positive B cell cross-match did not influence allograft survival. Autoantibodies were present only in renal recipients; they appeared to have a beneficial effect on allograft survival (P = 0.06). PRA > 10% appeared to have a detrimental effect on allograft survival in both renal (P = 0.07) and cardiac (P = 0.06) recipients. Since autoantibodies and PRA > 10% had opposing effects, the results of renal recipients were reanalyzed after omission of the recipients with autoantibodies and coexisting PRA > 10%. This resulted in augmentation of the protective effect for autoantibodies (P = 0.027) and of the detrimental effect for PRA > 10% (P = 0.020). Two-year survival curves showed that when autoantibodies coexisted with PRA > 10%, the long term, but not the short-term, detrimental effect of PRA > 10% was attenuated. Patients with a positive B cell cross-match clustered in the PRA > 10% group in both renal (PRA negative vs. PRA < 10%; P = 0.0251; PRA < 10% vs. PRA > 10%: P = 0.0011) and cardiac (PRA negative vs. PRA > 10%: P = 0.0085) recipients. We conclude that PRA > 10% is the best indicator to identify recipients at high risk for rejection, and that the influence of antibodies on graft survival can not reliably be established without taking coexisting antibodies into account.

Antilymphocyte Serum↗
PubMed1992

Epitope recognition in histone H1 by SLE autoantibodies in the presence of a DNA-ligand.

To investigate the specificity of anti H1 antibodies peptides from the N- and C-domain of H1 and the synthetic oligonucleotide (AT)6 were complexed. Circular dichroism (CD) spectroscopy indicated that the free peptides H1(1-16), H1(204-218) and C(121-210) in low salt buffer assume a random structure but become helical when bound to the oligonucleotide. The structured and unstructured H1 fragments were then analyzed by enzyme linked immunosorbent assay (ELISA) with anti-H1 antibodies in sera from patients with systemic lupus erythematosis (SLE) and with the monoclonal anti-H1 antibody MRA-12 derived from MLR lpr/lpr autoimmune mice. Binding of these antibodies to H1(204-218) and C was inhibited to a level of 50% when these H1 peptides were complexed with (AT)6. When the same antibody was tested with H1 fragment GC(34-210), attachment to oligonucleotide (AT)6 did not influence antibody binding. Competition studies with liquid phase GC and C antigen against solid phase GC and C indicated that liquid phase GC was more efficient in displacing antibody binding reactivity than liquid phase C. The displacement effect of both liquid phase antigens was greatest against solid phase C. We conclude that anti-H1 autoantibodies are directed against an epitope located near the junction of the G- and C-domain which is exposed and not masked when H1 is bound to DNA.

Autoantibodies↗
PubMed1984

T-cell subsets in the thyroids of mice developing autoimmune thyroiditis.

To examine the role of T-cell subsets in the development of thyroid lesions, female CBA/J mice were immunized with 60 micrograms mouse thyroglobulin (MTg) in 0.1 ml complete Freund's adjuvant in both hind footpads. The thyroids were removed 12-21 days later, pooled, and dispersed. The cell suspension was examined by membrane immunofluorescence for the distribution of Thy-1+, Lyt-1+, Lyt-2+, and sIg+ lymphocytes. For comparison, peripheral blood leukocytes (PBL) from the same animals were similarly examined. Throughout this 10-day interval, B cells in the thyroid were consistently below 5%, whereas B cells represented 19-24% of PBL. Thy-1+ cells in PBL ranged from 45 to 59%, whereas Thy-1+ cells in the thyroid were 37-50%. However, only thyroidal T cells showed a consistent decline with time and were replaced gradually by cells without T or B cell markers. In particular, there was a clear shift in the Lyt-1+:Lyt-2+ ratio from about 7 down to 2 in the thyroid as the early predominance of Lyt-1+ cells was followed by a relative increase in Lyt-2+ cells. Our results show that there is an accumulation of Lyt-1+ and Lyt-2+ cells in the infiltrated thyroid. These cells may include MTg-reactive, helper, and cytotoxic T cells which localize (or differentiate) in the thyroid and initiate the lesions.

Animals↗
PubMed1983

Experimental autoimmune thyroiditis. In vitro cytotoxic effects of T lymphocytes on thyroid monolayers.

Effector mechanisms in experimental autoimmune thyroiditis (EAT) were studied in vitro by establishing a cytotoxicity system with thyroid target cells. Lymph node cells (LNC) from popliteal and inguinal lymph nodes were obtained from CBA/J mice (8-10 wk old) 12-18 d after immunization with 120 micrograms mouse thyroglobulin (MTg) in complete Freund's adjuvant (0.2 ml to both hind footpads and thighs) and were cultured with MTg (10-50 micrograms/ml). On day 5 of culture, viable LNC were added to labeled thyroid monolayers and their cytoxicity was assayed after 16 h. Functional thyroid target cells, as reflected by MTg production for up to 9 d, were prepared by adding 1 mM dibutyryl adenosine 3',5'-cyclic monophosphate and 60 microU thyroid-stimulating hormone/ml to the culture medium. On days 5-7, confluent monolayers were labeled with 111In and used as targets. Specific 111In-release ranged from 56 to 85%. The cytotoxic response is MTg specific and H-2 restricted. Pretreatment of thyroid target cells with rabbit antiserum to MTg completely inhibited cytotoxicity. Pretreatment with mouse antiserum to either Kk or Dk products resulted in approximately 50% inhibition, whereas the combined use of both antisera led to total inhibition. No cytotoxicity was observed when control BALB/c thyroid cultures were the target cells. The kinetics of the expansion of Thy-1+ cytotoxic cells by in vitro exposure to MTg were then studied. The cytotoxic response required 5 d to develop and was abolished by treating LNC on day 4 with monoclonal antibody to Lyt-1.1, but not to Lyt-2.1, plus complement. In contrast, by day 5, cytotoxicity was abrogated by similar treatment with antiserum to Lyt-2.1, but not to Lyt-1.1. We conclude that cytotoxic cells derived from MTg-immunized mice are Lyt-2-bearing cells but require the presence of Lyt-1-bearing cells for their generation and/or differentiation.

Animals↗
PubMed1983

Protein antigens of Theileria parva macroschizonts and immune precipitation studies.

The proteins of purified macroschizonts from Theileria parva, T. lawrencei, and T. taurotragi were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The major proteins of all species had molecular weights of 120,000, 70,000, 65,000, 62,000, 55,000, 44,000, and 35,000. All further experiments were carried out with T. parva. Using 125I surface labelling it was established that proteins with molecular weights of 70,000, 50,000, and 44,000 were membrane constituents. Staphylococcus aureus protein A-mediated immune precipitation studies with 125I-labelled lysates of macroschizonts and a rabbit anti-macroschizont serum specifically recognized proteins with molecular weights of 120,000, 91,000, 70,000, 62,000, and 35,000. A small proportion of sera recovered from Theileria immune cattle specifically recognized proteins with molecular weights of 180,000 and 70,000 in macroschizont-lysates.

Animals↗
PubMed1982

Lack of reactivity of sera from Theileria parva-infected and recovered cattle against cell membrane antigens of Theileria parva transformed cell lines.

Sera from Theileria parva infected, recovered and rechallenged cattle were tested in complement-dependent cytotoxicity, membrane immunofluorescence and antibody-dependent cellular cytotoxicity assays for the presence of antibodies against cell membrane antigens of T. parva transformed cell lines. In the complement-dependent antibody-mediated cytotoxicity assay, sera from lethally infected animals were negative. Some recovered cattle showed a positive reaction, but such reactions were also observed when an eland cell line infected with T. taurotragi, and bovine lymphoblastoid cells were used as targets. Reaction was less against Ig-negative peripheral blood lymphocytes. Evidence is presented that these reactions could be evoked by attachment of immune complexes to Fc-receptors. It is concluded that cattle exposed to T. parva infection do not develop antibodies against specific T. parva (or T. parva-induced) cell surface antigens.

Animals↗
PubMed1981

Virus-specific cytotoxic activity to mammary tumor cells of sera from normal and tumor-bearing mice with inhibition at low dilutions.

Sera from normal mice and mice bearing murine mammary tumor virus (MTV)-induced tumors showed cytotoxic reactions to the MTV-producing Mm5mt/c1 cell line. The reaction could be blocked by the addition of MTV, but not of purified gp52 and p28. In sera from tumor bearers, cytotoxic responses ranged from 15 to 66%; reactivity was generally highest when the serum was diluted 32 to 128 times. The cytotoxic sera from the normal animals showed a much lower activity; again, there was a lack of cytotoxic response at lower serum dilutions. Low dilutions (1 to 64) of sera from tumor-bearing and normal mice were found to inhibit the MTV-specific cytotoxic activity of rabbit anti-MTV serum on the Mm5mt/c1 cell line. Specificity of this phenomenon was deduced from the fact that there was less inhibition by the mouse sera of anti-Rauscher leukemia virus-specific cytotoxic activity to Rauscher leukemia virus-infected cells and of anti-vaccinia virus serum to vaccinia virus-infected cells. Absorption of the mouse sera with rabbit anti-gp52 serum almost completely abolished the inhibition; after absorption with MTV, inhibition was somewhat reduced. The effect of free gp52 and MTV/anti-MTV immune complexes on the anti-MTV immune response is discussed.

Animals↗