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I Papp

Publications and source records attributed to I Papp.

At least 19 recordsLinked to original sources
PubMed1997

Molecular and cytogenetic analyses of stably and unstably expressed transgene loci in tobacco.

To study the influence of genomic context on transgene expression, we have determined the T-DNA structure, flanking DNA sequences, and chromosomal location of four independent transgene loci in tobacco. Two of these loci were stably expressed in the homozygous condition over many generations, whereas the other two loci became unstable after several generations of homozygosity. The stably expressed loci comprised relatively simple T-DNA arrangements that were flanked on at least one side by plant DNA containing AT-rich regions that bind to nuclear matrices in vitro. Of the unstably expressed loci, one consisted of multiple incomplete T-DNA copies, and the second contained a single intact T-DNA; in both cases, however, binary vector sequences were directly contiguous to a right T-DNA border. Fluorescence in situ hybridization demonstrated that the two stably expressed inserts were present in the vicinity of telomeres. The two unstably expressed inserts occupied intercalary and paracentromeric locations, respectively. Results on the stability of transgene expression in F1 progeny obtained by intercrossing the four lines and the sensitivity of the four transgene loci to inactivation in the presence of an unlinked "trans-silencing" locus are also presented. The findings are discussed in the context of repetitive DNA sequences and the allotetraploid nature of the tobacco genome.

Amino Acid Sequence↗
PubMed1996

Gene silencing mediated by promoter homology occurs at the level of transcription and results in meiotically heritable alterations in methylation and gene activity.

The promoter homology-dependent inactivation of a 35Spro-hygromycin phosphotransferase (hpt) gene, which is present at the H2 locus, by the multipurpose 271 silencing locus has been studied. The 271 locus can silence any gene under the control of the 35Spro as well as endogenous nitrite reductase (NiR) genes of tobacco because of the presence of a chimeric antisense gene (35Spro-RiN). All F1 progeny of a cross between homozygous H2 and 271 lines were sensitive to hygromycin and were chlorotic (a symptom of nitrogen deficiency). These phenotypes were accompanied by a reduction in the steady-state levels of Hyg and NiR transcripts. Transcriptional run-on experiments indicated, however, that while NiR silencing occurred post-transcriptionally, the hpt gene was inactivated at the transcriptional level; this was associated with increased methylation of the 35Spro of the hpt gene. NiR gene expression recovered uniformly to wild-type levels in first generation backcross (BC1) progeny that did not inherit the 271 locus. In contrast, hygromycin resistance was only partially and non-uniformly regained among adult BC1 plants. Moreover, substantial silencing of the hpt gene could persist into the BC2 generation. Genomic sequencing demonstrated that the meiotic heritability of hpt silencing in the absence of the 271 locus was correlated with cytosine methylation primarily at CpG and CpNpG residues. Despite this residual methylation, H2 loci weakened by an association with 271 did not acquire the ability to silence a 'naive' H2 locus. Fluorescence in situ hybridization revealed that the 271 locus was located at a telomere. The results strengthen the distinction between silencing effects involving homology restricted to coding or promoter regions, respectively. The former is a post-transcriptional process that is meiotically reversible; the latter is due to transcriptional inactivation and is associated with increased promoter methylation, which can lead to meiotically heritable reductions in target gene activity. The relevance of these data for the meiotic heritability of silencing, the non-transferability of silencing activity, and the basis of 271 silencing effects is discussed.

Antisense Elements (Genetics)↗
PubMed1996

Structural instability of a transgene locus in tobacco is associated with aneuploidy.

This paper describes molecular and cytogenetic evidence for the stability of a transgene locus that is present on the triplicated chromosome in an aneuploid tobacco line. This instability was manifested in several ways in trisomics including a major chromosome rearrangement that was detectable cytogenetically, smaller scale DNA rearrangements that occurred both germinally and somatically, and methylation/epigenetic silencing. In a deletion derivative of the locus, DNA breakpoints were found in AT-rich regions. One of these regions binds to nuclear scaffolds in vitro, suggesting a possible role for aberrant topoisomerase II cleavage in destabilization of the locus. The implications of increased chromosome instability in aneuploids for plant karyotype evolution and human carcinogenesis are discussed.

Aneuploidy↗
PubMed1996

[Practical experiences in the therapy of postweaning edema disease in piglets].

In a field trial 23 weeks old weaned piglets were orally inoculated with E. coli O139 K12 H1. The piglets received the same food and were kept under the same management regime. They were selected randomly into four groups and treated after the first clinical signs of CNS involvement of edema disease as follows during three days: Group 1: received a single daily i.m. application of 4 mg/kg body weight Melperone. Group 2: received a single daily i.m. application of 2 mg/kg body weight Amperozide. Group 3: was treated orally (intranasally) with 2 mg/kg body weight Amphetamin in a single daily application. Group 4: untreated control. The following parameters were evaluated before the begin of the therapy (day 0-4). A: Occurrence of diarrhea in a group B: Food consumption per piglet per day C: Death of piglets per group After the begin of the therapy (day 5-32) D: Death of piglets per group E: Average daily feed intake per piglet The results showed that the Melperone and Amphetamin treatment was superior regarding all examined parameters when compared to Amperozide treatment and to the control group.

Amphetamine↗
PubMed1995

High-frequency occurrence of virus-like particles with double-stranded RNA genome in Fusarium poae.

Fifty-five geographically different strains of Fusarium poae were assayed for the presence of extrachromosomal nucleic acid elements. All strains were found to harbour double-stranded RNA (dsRNA) elements and encapsidated virus-like particles (VLP). There were great individual differences in dsRNA patterns of the various strains, but numbers and sizes characteristic for a given isolate remained unchanged after repeated subculturing of the fungi. Morphological alterations or signs of degeneration were not observed in dsRNA-containing isolates. This is the first report on the ubiquitous occurrence of dsRNAs in a hyphomycete fungus species.

Fusarium↗
PubMed1994

Inheritance and expression of a transgene insert in an aneuploid tobacco line.

A T-DNA locus comprising nptII, uidA and nos genes--all under the control of the nos promoter (this locus was designated K because it encodes resistance to Kanamycin)--was found to be inherited erratically in a transgenic tobacco line. This anomalous behavior was partially explained following a karyotype analysis of plants representing several generations: these plants were aneuploids, presumably for the K-containing chromosome. During four generations of sexual propagation, transgenic plants that were either trisomic or tetrasomic for the K-containing chromosome (i.e. 2n = 49 or 2n = 50, respectively) were obtained. The trisomic plants (2n = 48 + 1) were virtually indistinguishable phenotypically from normal euploids (2n = 4x = 48), whereas the tetrasomic plants (2n = 48 + 2) were smaller, had somewhat misshapen leaves and exhibited reduced fertility. Although the amount of NPTII protein in different trisomic (K--, KK-, KKK) and tetrasomic (KK--, KKK-) plants was generally consistent with a K dosage effect, the genetic behavior of each trisomic--with respect to segregation of KanR and marker gene activity in progeny--was unique and not completely explicable by invoking aneuploidy. Specifically, unexpected gains or losses of K could occur, suggesting the formation of double reductional gametes and/or frequent gene conversion at this locus. The susceptibility of K locus marker genes to trans-inactivation in the trisomic and tetrasomic lines was tested by crossing in partially homologous silencing loci. In all transgenotypes tested, the three K marker genes were sensitive to trans-silencing, which was accompanied by methylation in all copies of the nos promotor. In addition to this directed inactivation/methylation, the K locus could also undergo infrequent, spontaneous partial methylation, which produced stable epialleles. In most plants, however, the multiple copies of the nos promoter at this locus remained unmethylated and active through four generations in all transgenotypes examined. The significance of these results for irregular inheritance patterns, aneuploid syndromes and homology-dependent gene silencing is discussed.

Aneuploidy↗
PubMed1993

CD4 mAb therapy modulates alloantibody production and intracardiac graft deposition in association with selective inhibition of Th1 lymphokines.

The accelerated (24 h) rejection of (LEWxBN)F1 cardiac allografts (Tx) in LEW rats sensitized with BN skin grafts, is abrogated with CD4 mAb (BWH-4) administration between skin (day -7) and heart (day 0) transplantation (Tx survival ca. 11 days, p < 0.0001). This study analyzed the effects of CD4-targeted therapy upon host IgG and IgM alloantibody (allo-Ab) within the serum by two-color flow cytometry, and within the Tx, by immunohistology. These data were correlated with mRNA and protein production profiles of Th1 (IL-2, IFN-gamma) vs Th2 (IL-4) specific cytokines (polymerase chain reaction and/or immunohistology). Skin grafts elicited a strong systemic IgM allo-Ab response, which peaked at the time of cardiac Tx rejection at 24 h. It was associated with extensive deposits of IgM on Tx endothelium. Treatment with BWH-4 mAb diminished circulating IgM allo-Ab levels, and only low levels of IgM could be detected at the Tx site. Conversely, the low circulating IgG allo-Ab levels during rejection at 24 h in untreated recipients were accompanied by a strong labeling for intra-Tx IgG. BWH-4 mAb therapy did not prevent totally the switch of the IgM to IgG, but the IgG allo-Ab response was earlier, less intense and more transient than in untreated recipients. Accelerated rejection triggered sequential lymphokine mRNA expression in cardiac Tx, with the peak of transcription for IL-2 (6-12 h) preceding that for IL-4 (24 h). Interestingly, although CD4 targeted therapy virtually ablated the induction of IL-2 mRNA, it preserved transcription of the IL-4 gene. BWH-4 mAb therapy decreased otherwise abundant intra-Tx IL-2 and IFN-gamma, but allowed a vigorous elaboration of IL-4, confirming the translation of mRNA to the protein in vivo. Thus, CD4 mAb-mediated abrogation of accelerated cardiac Tx injury correlates with suppression of Th1 responses (depressed IL-2 and IFN-gamma production), but sparing of the Th2 function (enhanced IL-4 elaboration). Indeed, CD4 mAb-induced allo-Ab depression and immunosuppressive effects may reflect selective targeting of proinflammatory Th1-like cells and the multifaceted effects of IL-4 produced by unopposed Th2-like cells.

Animals↗
PubMed1993

The bacterial attachment site of the temperate Rhizobium phage 16-3 overlaps the 3' end of a putative proline tRNA gene.

Bacteriophage 16-3 inserts its genome into the chromosome of Rhizobium meliloti strain 41 (Rm41) by site-specific recombination. The DNA regions around the bacterial attachment site (attB) and one of the hybrid attachment sites bordering the integrated prophage (attL) were cloned and their nucleotide sequences determined. We demonstrated that the 51 bp region, where the phage and bacterial DNA sequences are identical, is active as a target site for phage integration. Furthermore it overlaps the 3' end of a putative proline tRNA gene. This gene shows 79% similarity to the corresponding proline tRNA-like genomic target sequence of certain integrative plasmids in Actinomycetes.

Attachment Sites, Microbiological↗
PubMed1992

[Clinical pathology of gastric mucosal dysplasia].

The stomach cancer develops on dysplastic lesions of gastric mucosa. It can be found in every precancerous condition, as chronic gastritis, gastric adenoma, giant rugal hypertrophy, chronic peptic ulcer, gastric stump after partial resection, pernicious anaemia. So, this dysplastic change is not a specific lesion. Different classifications are known for grading of gastric dysplasia. Authors evaluated them compared with each other. The signs of dysplasia were studied in 306 gastric aimed biopsy specimens from 233 patients between 1979-1990. In this material severe dysplasia occurred in 20.6%. It means a frequency of 0.84% regarding all gastric endoscopies in the same period of time. The endoscopic investigation revealed a protruded lesion in 18.5% and excavated one in 45.9%. What is very important, local change could not be detected in 35.6%. Follow-up study could be performed in 49 patients in a period of 1-7 years. In this group cancer developed in five patients. By the other hand, 22 gastric carcinomas were proved amongst 233 patients. The authors' recommendation is to follow-up the patients bearing gastric dysplasia at least during 10 years after the diagnosis.

Diagnosis, Differential↗
PubMed1992

[Diagnostic possibilities of endoscopic ultrasonography in the detection of gastric cancer].

After conventional gastroscopy and biopsy the endoscopic ultrasonography (EUS) was performed in 115 patients with gastric ulcer and carcinoma. The markers of benignity and malignity were analyzed by EUS, and the criteria of benign and malign excavated lesions were described. On the base of endoscopic pictures 3 groups of gastric excavations were distinguished, and the recorded images of this excavations were reevaluated. Benign ultrasonic markers were detected in one case of excavated tumors, in 54% in group of ulcers with suspicion of malignity and in 82% in cases of benign ulcers. Authors evaluate the cause of overestimate. Ten cases of early gastric cancers are reported. Authors believe that the endosonographic examinations of the stomach are valuable in detecting and stating of gastric carcinoma.

Diagnosis, Differential↗
PubMed1992

Evidence for functional heterogeneity of rat CD4+ T cells in vivo. Differential expression of IL-2 and IL-4 mRNA in recipients of cardiac allografts.

The in vivo relevance of functional dichotomy of CD4+ Th clones was studied by analyzing the induction of mRNA encoding for Th1- (IL-2) and Th2- (IL-4) specific lymphokines in a model of accelerated (24 h) cardiac allograft (Tx) rejection in presensitized rats. The polymerase chain reaction-assisted screening of total cellular RNA from cardiac Tx of otherwise untreated sensitized recipients has revealed sequential lymphokine mRNA expression, with the peak of IL-2 mRNA (6-12 h) preceding that for IL-4 mRNA, which was maximal at the time of actual Tx loss (24 h). Both IL-2 and IL-4 transcripts could be readily detected by polymerase chain reaction analysis in the spleens during the course of accelerated rejection. Treatment of prospective cardiac Tx recipients with BWH-4, a mouse anti-rat CD4 mAb, abrogated rejection at 24 h and prolonged cardiac Tx survival to ca. 11 days, coinciding with significantly diminished IL-2 mRNA expression. In contrast, CD4 targeted therapy preserved intra-Tx and splenic transcription of the IL-4 gene. Spleen lymphocytes from mAb-conditioned recipients separated by magnetic microspheres into phenotypically distinct subpopulations, showed differential induction of IL-2 and IL-4 mRNA. Thus, IL-2 mRNA was at most very weakly expressed, whereas IL-4 transcription was strongly induced both in CD4+ T cells and its OX-22- subset. This study demonstrates the induction of IL-4 mRNA in situ in the rat system, describes discordant elaboration of IL-2 and IL-4 mRNA in untreated/anti-CD4 mAb-treated cardiac Tx recipients, and identifies OX-22- CD4+ T cells as the IL-4 mRNA producers. Thus, these results provide evidence for functional heterogeneity of rat CD4+ T cells in vivo, as defined by divergent mRNA lymphokine transcription profiles.

Animals↗
PubMed1990

[Esophageal and gastric candidiasis].

The authors examined the morbidity rate of mycotic diseases of stomach and esophagus. There were 746 biopsian and abrasian cytologic samplings carried out in a year and 12.3% of the cases turned out to be positive. Comparing the two sampling patterns the abrasian cytology has proved to be more effective. The prevalence of candidiasis was found to be higher in case of malignant diseases. In states accompanied by low acid values (as in case of patients under H2-receptor blocking--treatment) mycotic infection proved to be more frequent, too.

Candidiasis↗
PubMed1990

Early detection of colorectal cancer. Preliminary report on the prospective value of a combined screening method for occult rectal bleeding.

The authors have developed a specific, sensitive, simple and economic method for the detection of occult colorectal bleeding. The new technique consists of the traditional guaiac type reaction and an immunochemical test which as a second-phase test using dried filter paper discs serves to eliminate or reduce the false-positive reactions, decreasing the necessity of further invasive diagnostic measures. They report on their experience obtained with the screening of a rural population of 3,346 persons; a positive colour reaction was observed in 546 individuals (16.3%) who were not on diet. In the second-phase immunochemical examination, however, this number decreased to 54 (1.6%). In this group of patients, who did have blood in their stools, 5 colorectal carcinomas (9.25%), each in the early Duke stage A, could be detected. The overall detection rate of carcinoma, polyp and colitis ulcerosa, likewise a precancerous state, was 40.73%. The results obtained so far suggest that this combined screening method represents an easier, cheaper and a more rapid diagnostic method for the detection of early colorectal carcinomas and precancerous states compared to the conventional ones. In mass screening the treatment and transportation of the test specimens are simple and hygienic.

Aged↗