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J Plachy

Publications and source records attributed to J Plachy.

At least 19 recordsLinked to original sources
PubMed2001

CpG island protects Rous sarcoma virus-derived vectors integrated into nonpermissive cells from DNA methylation and transcriptional suppression.

CpG islands are important in the protection of adjacent housekeeping genes from de novo DNA methylation and for keeping them in a transcriptionally active state. However, little is known about their capacity to protect heterologous genes and assure position-independent transcription of adjacent transgenes or retroviral vectors. To tackle this question, we have used the mouse aprt CpG island to flank a Rous sarcoma virus (RSV)-derived reporter vector and followed the transcriptional activity of integrated vectors. RSV is an avian retrovirus which does not replicate in mammalian cells because of several blocks at all levels of the replication cycle. Here we show that our RSV-derived reporter proviruses linked to the mouse aprt gene CpG island remain undermethylated and keep their transcriptional activity after stable transfection into both avian and nonpermissive mammalian cells. This effect is most likely caused by the protection from de novo methylation provided by the CpG island and not by enhancement of the promoter strength. Our results are consistent with previous finding of CpG islands in proximity to active but not inactive proviruses and support further investigation of the protection of the gene transfer vectors from DNA methylation.

Adenine Phosphoribosyltransferase↗
PubMed2000

A large database of chicken bursal ESTs as a resource for the analysis of vertebrate gene function.

Chicken B cells create their immunoglobulin repertoire within the Bursa of Fabricius by gene conversion. The high homologous recombination activity is shared by the bursal B-cell-derived DT40 cell line, which integrates transfected DNA constructs at high rates into its endogenous loci. Targeted integration in DT40 is used frequently to analyze the function of genes by gene disruption. In this paper, we describe a large database of >7000 expressed sequence tags (ESTs) from bursal lymphocytes that should be a valuable resource for the identification of gene disruption targets in DT40. ESTs of interest can be recognized easily by online or keyword searches. Because the database reflects the gene expression profile of bursal lymphocytes, it provides valuable hints as to which genes might be involved in B-cell-specific processes related to immunoglobulin repertoire formation, signal transduction, transcription, and apoptosis. This large collection of chicken ESTs will also be useful for gene expression studies and comparative gene mapping within the chicken genome project. Details of the bursal EST sequencing project and access to database search forms can be found on the DT40 web site (http://genetics.hpi.uni-hamburg.de/dt40.html).

Animals↗
PubMed1998

Genes of chicken MHC regulate the adherence activity of blood monocytes in Rous sarcomas progressing and regressing lines.

The influence of the chicken major histocompatibility (B) complex (MHC) on the adherence potential of monocyte-derived macrophages was examined using the congenic chicken lines CB and CC. These lines represent well-defined genetic models for the study of resistance (CB) or susceptibility (CC) to the progressive growth of Rous sarcomas. Using a monoclonal antibody specific for chicken monocytes/macrophages, CB and CC chickens were shown by flow cytometry analyses to have similar proportions of peripheral blood monocytes. However, when the glass-adherence potential of these cells was compared during incubation in tissue culture medium over 24, 48 and 72 h at 40 degrees C, significant differences were seen between cells from these two inbred lines. After 24 and 48 h, glass-adherence by CB cells was 2-3 fold higher than that of CC cells. After 72 h this difference decreased to 1.5 fold. At 24 and 48 h, the adherent CB macrophages also appeared about 1.5 times larger than those of CC chickens. Genetic analysis using F1 hybrids (CBxCC) showed that this trait is regulated by a dominant gene that segregates with the B12 haplotype in the backcross generation F1xCC. From the results obtained with the recombinant congenic lines CB.R1 and CC.R1, we conclude that the gene regulating adherence potential is localized within the B-F/L region of the chicken MHC. About 50% of adherent cells were able to phagocytose opsonised FITC-labelled Zymosan particles. The level of nitric oxide production in vitro by CB and CC macrophages was equal. The importance of cells of the mononuclear phagocyte system for the response to Rous sarcoma virus (RSV) infection was studied in CB chickens using the anti-macrophage agents silica, carrageenan, and C12MDP, encapsulated in liposomes. In those chickens treated with silica and carrageenan, we observed progressive growth of RSV-induced tumors. The graft-versus-host reactivity of peripheral blood lymphocytes (PBL) of treated chickens was comparable to controls. In vitro nitric oxide production by macrophages from silica-treated chickens was higher than by macrophages from untreated controls.

Animals↗
PubMed1996

Phenotypic changes induced by wild type and variant c-src genes carrying C-terminal sequence alterations.

We previously reported the isolation of PR2257, a novel avian sarcoma retrovirus which transduced the c-src protooncogene. The v-src gene of PR2257 differs from the c-src gene by a sequence change after amino acid 525, resulting in the replacement of tyrosine 527 by a valine, and an extension of the open reading frame into the non coding region of c-src. We investigated the respective roles of Tyr527 mutation and of the C-terminal extension in activating the oncogenic properties of c-src. Therefore we overexpressed the wild type c-src gene and c-src variants, carrying either a substitution of tyrosine 527 or an extension of the C-terminus or both modifications in combination, in chicken embryo fibroblasts and post mitotic neuroretina (NR) cells, using replication defective retroviruses. We also used in vivo inoculation of plasmid DNA to assess the tumorigenicity of the various c-src genes. We report that, in contrast to previous results, overexpression of c-src is sufficient to induce NR cell division. While mutation of tyrosine 527 alone significantly activates c-src transforming and tumorigenic properties, its combination with the C-terminal extension of PR2257 confers to this gene full oncogenic properties and increased metastatic potential as compared to the v-src of Rous sarcoma virus strains.

Animals↗
PubMed1996

Influence of the transduced 3'UTR of the c-src oncogene on tumour growth induced by the v-src gene of avian sarcoma virus PR2257.

Avian sarcoma virus PR2257 contains 952 bp transduced from the left part of the 3'UTR of the chicken c-src oncogene. Deletion mutants were constructed to determine the effect of the 3'UTR on tumorigenicity in vivo and in vitro. In the presence of the 3'UTR, tumours were 3.4 times larger in vivo, and tumorigenicity was increased 2.5-fold in vitro. Several regulatory submotifs were also found within the 3'UTR. Parts of the 3'UTR were cloned into the LTR CAT plasmid and analysed for CAT expression. A 170 bp element was found to be responsible for the enhanced expression of the CAT gene. These results demonstrate the effect of the transduced 3'UTR sequence during long-term interaction between PR2257 virus and the chicken genome, and suggest a novel regulatory mechanism of the src oncogene.

Animals↗
PubMed1996

Formulation of controlled release drug preparations with antacid effect.

Opportunities for the formulation of long-acting antacid preparations were demonstrated summarizing the results of pharmaceutical technological experiments. The telemetric intragastric data were in correlation with the in vitro measurements and demonstrated the significantly higher bioavailability of long-acting antacid preparations.

Antacids↗
PubMed1996

[Role of mass transfer processes in drug formulation].

Authors call attention on the possibilities that drug release from solid preparations can be influenced by solubility and dissolution rate according to the clinical requirements regarding the duration of action. The therapeutic time interval may be modulated influencing the rate of absorption by controlling dissolution rate and changing the transport through the membranes. The results obtained from dissolution, absorption and efficacy studies of the evaluated active substances (magnesium oxide, metoprolol, nitrofurantoin) demonstrate the significance of mass transfer processes in the drug formulation.

Dosage Forms↗
PubMed1995

In vitro biopharmaceutical investigation of antacid activity in standard dissolution test apparatus.

The pH stat titration and the Rossett-Rice test used especially for the reaction kinetical and in vitro biopharmaceutical investigation of antacids were standardized applying the U.S.P. Dissolution Test Apparatus with paddle stirring element. The developed "artificial stomach" is suitable to simulate also the gastric emptying. The in vitro model may give a new alternative for the in vitro evaluation of antacid effectiveness, because this standardized method may perfectly eliminate the deficiencies of the earlier test prescriptions.

Aluminum Hydroxide↗
PubMed1995

Vaccination with a low-oncogenic strain of Rous sarcoma virus prevents visceral tumors in chickens.

The oncogenic potential of different strains of Rous sarcoma virus (RSV) varies significantly in two Mhc(B) congenic chicken lines CB and CC and in their F1 hybrids with the unrelated inbred line IA. The Bryan high-titer pseudotype of RSV of antigenic subgroups D and B (BH-D, and BH-B) was highly oncogenic, eliciting mostly fatal, progressively growing tumors. Visceral tumor formation and erythroblastosis were seen after challenge with BH-B in CB and CC chickens, but not in their F1 hybrids with IA. Tumor regression induced by a low-oncogenic RSV strain PR-C elicited a protective immunity capable of preventing not only the progressive growth of challenge tumors at the site of inoculation, but also visceral tumor formation and erythroblastosis.

Animals↗
PubMed1992

Biology of the chicken MHC (B complex).

The major histocompatibility complex (MHC) of chicken is the B complex, originally described as a blood group system. Its three classes of cell membrane antigens have been clearly defined by serological, histogenetic, biochemical, and molecular biological methods. Two of these classes are homologous to classes I and II of mammals (B-F and B-L respectively), while the third--B-G antigen--has not so far been detected in mammals. The possible role of this antigen is discussed. The genes of the MHC play important roles in the regulation of immune response, disease resistance, and regression of Rous sarcomas.

Animals↗
PubMed1991

Graft versus host reaction induced by thymectomized and bursectomized chicken blood.

Graft versus host reaction in chicken embryos was induced by blood taken from thymectomized or bursectomized or nonoperated donors. The intensity of graft versus host reaction induced by the blood of thymectomized chickens was increased comparing to the reaction induced by blood from control donors. No such result was recorded when the blood donors had the bursa of Fabricius removed.

Animals↗
PubMed1987

Biopharmaceutical investigation of fenoprofen.

The salts of fenoprofen formed with different metals have shown various crystal forms and solubility. The calcium salt has proved the most suitable characteristics for tablet and capsule production. Dissolution and absorption parameters of this substance were studied using in vitro and in vivo methods. The absorption rate and the correlation between pH and membrane diffusion rate constant were investigated in vitro using the "Sartorius" apparatus. The dissolution rate--depending on pH--was investigated by the oscillometric method. The in vivo disintegration of an experimental sample was compared with a commercial preparation. The comparison has been documented by endoscopic photography.

Biopharmaceutics↗