Biomedical subjects

P Svec

Publications and source records attributed to P Svec.

At least 91 records · Page 5Linked to original sources

PubMed1985

Diversity of circumsporozoite antigen genes from two strains of the malarial parasite Plasmodium knowlesi.

The complete nucleotide sequence of the coding region of the circumsporozoite antigen gene (CS gene) of the Nuri strain of the malarial parasite Plasmodium knowlesi is presented. The gene from the Nuri strain exhibits a novel form of sequence diversity when compared to the CS gene from the H strain. Instead of the 12 tandem repeating 36-base pair units of the H strain, the Nuri strain contains 16 tandem repeating 27-base pair units of a different nucleotide sequence that encodes a different repeating peptide. In contrast, the 5' and 3' coding and noncoding sequences flanking the repeats are 98 percent conserved in both strains.

Amino Acid Sequence↗

PubMed1985

Comparison of left-end DNA sequences of bacteriophages Mu and D108.

The nucleotide sequences of the left ends of bacteriophage Mu DNA and that of its close relative D108 have been determined. The first 100 bp of phages Mu and D108 are substantially the same except for an octanucleotide change from bp 53 to 61 and other small interspersed base-pair changes from bp 61 to 200. The first five host nucleotides preceding the host-phage junction are generally, but not always, G + C-rich and these five nucleotides display no obvious consensus sequence. Both phages Mu and D108 share striking similarity in their end DNA sequences to the end sequences of the newly described Escherichia coli movable genetic element IS30.

Bacteriophage mu↗

PubMed1984

Structure and organization of genes for sporozoite surface antigens.

The major surface antigen (circumsporozoite-protein) of the sporozoite stage of Plasmodium knowlesi has been cloned and characterized. The gene is notable for the presence of a 36 base pair unit repeated in tandem 12 times. These repeats may function at the DNA level in regulating gene expression and at the protein level in providing multiple copies of a single epitope (repitope) as part of a protein designed to evade and decoy the immune system.

Amino Acid Sequence↗

PubMed1983

Structure of the plasmodium knowlesi gene coding for the circumsporozoite protein.

The gene that codes for the surface antigen of Plasmodium knowlesi sporozoites (CS protein) is unsplit and present in the genome in only one copy. The CS protein, as deduced from DNA sequence analysis of the structural gene, has an unusual structure with the central 40% of the polypeptide chain present as 12 tandemly repeated amino acid peptide units flanked by regions of highly charged amino acids. The protein has an amino-terminal hydrophobic amino acid signal sequence and a hydrophobic carboxy-terminal anchor sequence. The coding sequence of the gene has an AT content of 53%, compared with 70% AT in the 5' and 3' flanking sequences, and is contained entirely within an 11 kb Eco RI genomic DNA fragment. This genomic fragment expresses the CS protein in E. coli, indicating that the parasite promoter and ribosome binding site signals can be recognized in E. coli.

Amino Acid Sequence↗

PubMed1982

Role of natural prostaglandins in the control of murine mammary tumor virus expression.

The regulation of murine mammary tumor virus (MuMTV) production by mammotropic hormones, hormonomimetic substances, and cyclic nucleotides was investigated. The virus produced in control and treated mammary tumor cell cultures was quantitated by measuring the supernatant reverse transcriptase activity in exogenous reaction using poly(rC).oligo(dG) as template-primer. Two days after exposure, the synthetic glucocorticoid, dexamethasone (DXMT), increased spontaneous MuMTV production at optimal concentration (0.1 mumol) up to ten times. Dibutyryl derivative of cyclic AMP had no effect on spontaneous MuMTV production, whereas the drug potentiated suboptimal concentrations of the glucocorticoid. Natural prostaglandins, potent agonists of adenylate cyclase catalyzing intracellular synthesis of cyclic AMP, enhanced both basal (up to five times) and DXMT-stimulated (up to 1.6 times) MuMTV replication. The MuMTV-stimulating activity of prostaglandins decreased in the order of PGA1 greater than PGE1 greater than PGB1 greater than PGF2 alpha. Prostaglandins can be replaced partially by norepinephrine and isoproterenol by enhancing the DXMT-mediated MuMTV stimulation, whereas these drugs remained without effect on spontaneous MuMTV production. Theophylline, an antagonist of cAMP-phosphodiesterase converting cAMP to AMP, enhanced the virus-stimulating activity of DXMT as well as of prostaglandins. The enhancement of MuMTV production by adenylate cyclase agonists do not correlate absolutely with the estimates of intracellular cAMP levels, since the highest amounts of cAMP has been repeatedly observed in cells treated with PGE1 and norepinephrine. The results indicate that besides hormones, other hormone-like substances and cyclic nucleotides may be involved in the complex mechanism of hormone-regulated MuMTV genome expression.

Adenocarcinoma↗

PubMed1982