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Biomedical subjects

G H Veeneman

Publications and source records attributed to G H Veeneman.

At least 19 recordsLinked to original sources
PubMed2001

Revised interpretation of the immunological results obtained with pneumococcal polysaccharide 17F derived synthetic di-, tri- and tetrasaccharide conjugates in mice and rabbits.

Recently, the structure for pneumococcal polysaccharide (PS) 17F has been revised. Based on the former PS structure, immunogenicities of PS 17F derived synthetic di-, tri- and tetrasaccharide conjugates have been reported in mice. Here, we present additional data on the immunogenicities of these conjugates in rabbits and re-evaluate the immunogenicity results in the light of the revised PS 17F structure.

Animals↗
PubMed1999

Tyrosine kinase activity of purified recombinant cytoplasmic domain of platelet-derived growth factor beta-receptor (beta-PDGFR) and discovery of a novel inhibitor of receptor tyrosine kinases.

Aberrant expression of platelet-derived growth factor and its receptor (PDGFR) has been implicated in various human disorders, including cardiovascular disease and certain types of cancer. Inhibitors of the tyrosine kinase activity of PDGFR are leads in the development of novel agents to combat these diseases. We describe here a novel, potent inhibitor of PDGFR tyrosine kinase, 3-(4-dimethylamino-benzylidenyl)-2-indolinone (DMBI). The compound also inhibits signal transduction through fibroblast growth factor receptor 1 (FGFR1), but is not active towards epidermal growth factor receptor (EGFR) or c-Src tyrosine kinase. The activity of DMBI and other tyrosine kinase inhibitors was compared in a cell-based assay as well as in an assay based on purified recombinant platelet-derived growth factor beta-receptor (beta-PDGFR) lacking the transmembrane and ligand-binding domain. We showed that this truncated beta-PDGFR could dimerize, and that dimerization was required for tyrosine kinase activity. Tyrosine kinase activity was modulated by inhibitors of beta-PDGFR autophosphorylation in cells, but not by specific inhibitors of EGFR or c-Src tyrosine kinase. We conclude that beta-PDGFR lacking the transmembrane and ligand-binding domain retains the essential properties of the full-length receptor tyrosine kinase.

3T3 Cells↗
PubMed1994

Alpha-sialyl cholesterol increases laminin in Schwann cell cultures and attenuates cytostatic drug-induced reduction of laminin.

Schwann cells play an important role in peripheral nerve regeneration. Here, we report the effect of alpha-sialyl cholesterol (alpha-SC), a derivative of the sialic acid-containing natural gangliosides, and the cytostatic agents, cisplatin, taxol and vincristine on the laminin production in Schwann cell cultures isolated from rat sciatic nerves. Laminin, one of several extracellular matrix components produced by Schwann cells, is known to potentiate axonal outgrowth. Laminin content was increased by alpha-SC, starting at 7.0 micrograms/ml with a maximal effect at 22.4 micrograms/ml (30%, P < 0.001). The three cytostatic drugs, dose-dependently reduced laminin content in Schwann cell cultures: (1) cisplatin at a threshold dose of 2 micrograms/ml (-26.4%, P < 0.001); (2) taxol, starting at a dose of 1 ng/ml (-8.0%, P < 0.05); and (3) vincristine, starting at 0.5 ng/ml (-5.9%, P < 0.05). Cultured Schwann cells were incubated with cytostatic drugs in combination with increasing amounts of alpha-SC and it was found that, depending on the cytostatic drug concentration used, alpha-SC could reduce or completely prevent the cytostatic drug-induced reduction of laminin in Schwann cell cultures. Co-treatment with alpha-SC also reduced part of the morphological changes caused by the cytostatic drugs. alpha-SC did not counteract the anti-proliferative effect of the cytostatic drugs on K-562 human erythroleukemia cells. In conclusion, alpha-SC increased laminin content in Schwann cell cultures and protected Schwann cell cultures against the decrease of laminin by cytostatic drugs without interfering with the anti-proliferative potential, suggesting that alpha-SC may have clinical use in protecting cancer patients against the neurotoxic effects of cytostatic drugs.

Animals↗
PubMed1993

Iodonium ion-assisted synthesis of a haptenic tetrasaccharide fragment corresponding to the inner cell-wall glycopeptidolipid of Mycobacterium avium serotype 4.

Condensation of ethyl 2,4-di-O-benzoyl-1-thio-alpha-L-rhamnopyranoside with ethyl 3-O-benzyl-4-O-chloroacetyl-2-O-methyl-1-thio-beta-L-fucopyranoside in the presence of iodonium di-sym-collidine perchlorate afforded exclusively ethyl 2,4-di-O-benzoyl-3-O-(3-O-benzyl-4-O- chloroacetyl-2-O-methyl-alpha-L-fucopyranosyl)-1-thio-alpha-L-rhamnop yra noside. This disaccharide derivative was extended at C-1 with 3-benzyloxycarbonylaminopropyl 6-deoxy-3,4-O-isopropylidene-alpha-L- talopyranoside, using N-iodosuccinimide and triflic acid as the catalyst, to furnish 3-benzyloxycarbonylaminopropyl 6-deoxy-2-O-[2,4-di-O-benzoyl-3-O-(3-O-benzyl-4-O-chloroacetyl-2-O-me thy l- alpha-L-fucopyranosyl)-alpha-L-rhamnopyranosyl]-3,4-O-isopropylidene-alp ha-L- talopyranoside (20). Selective removal of the chloroacetyl group from 20, followed by condensation with ethyl 2,3-di-O-benzoyl-4-O-methyl-1-thio-alpha-L- rhamnopyranoside in the presence of the same thiophilic promoter, yielded a fully protected tetrasaccharide derivative. Deprotection of the latter gave the target compound 3-aminopropyl 6-deoxy-2-O-[3-O-[2-O- methyl-(4-O-methyl-alpha-L-rhamnopyranosyl)-alpha-L-fucopyranosyl]-alpha -L- rhamnopyranosyl]-alpha-L-talopyranoside (1).

Carbohydrate Sequence↗
PubMed1993

Protein-conjugated synthetic di- and trisaccharides of pneumococcal type 17F exhibit a different immunogenicity and antigenicity than tetrasaccharide.

Overlapping synthetic disaccharide, trisaccharide and tetrasaccharide, derived from pneumococcal polysaccharide type 17F (PS17F), were coupled to keyhole limpet haemocyanin (KLH). The conjugates were tested in mice. The disaccharide-KLH and especially trisaccharide-KLH, in combination with Quil A, induced high titres of high-avidity anti-PS17F IgG. Both conjugates protected mice against challenge with Streptococcus pneumoniae 17F. Tetrasaccharide-KLH, although able to elicit anti-tetrasaccharide antibodies, induced a minimal non-protective anti-PS17F IgG response of low avidity. The tetrasaccharide-KLH conjugate, in contrast to the other conjugates, failed to bind rabbit anti-PS17F IgG.

Animals↗
PubMed1992

Detection of Aspergillus and Penicillium extracellular polysaccharides (EPS) by ELISA: using antibodies raised against acid hydrolysed EPS.

Species of the fungal genera Aspergillus and Penicillium produce immunologically active extracellular polysaccharides (EPS) in which galactofuranose residues are immunodominant. The antigenic determinant of the EPS of A. fumigatus, A. niger and P. digitatum could be removed by acid hydrolysis. Due to the hydrolysis of the EPS the immunological reaction between IgG anti-native EPS and hydrolysed EPS disappeared. Antibodies raised in rabbits against the acid hydrolysed EPS revealed new antigenic determinants that were exposed as a result of the acid hydrolysis. Immunological inhibitory experiments showed that the antibodies were no longer directed to galactofuranose residues. Enzyme Linked Immunosorbent Assay, carried out with antibodies raised against the acid hydrolysed EPS showed that the antibodies against the acid hydrolysed EPS were more species specific in comparison with the antibodies against the native EPS.

Animals↗
PubMed1989

Synthesis of a substrate of protein kinase C and its corresponding phosphopeptide.

The syntheses of a protein kinase C (PKC) peptide substrate, H-Lys-Arg-Thr-Leu-Arg-OH, and a phosphopeptide analog of the synthetic substrate, H-Lys-Arg-Thr(P)-Leu-Arg-OH, are reported. PKC phosphorylates the peptide with an apparent KM of 0.30 +/- 0.04 mM and an apparent Vmax equal to one-tenth that of histone III-S. The synthesis of the phosphopeptide features a recently developed convenient phosphorylation procedure for serine and threonine using N,N-diethylamino-dibenzylphosphoramidite. A complete characterization of the PKC substrate and its corresponding phosphopeptide by C-H COSY 2D n.m.r. is included.

Chemical Phenomena↗
PubMed1988

(1----5)-linked beta-D-galactofuranosides are immunodominant in extracellular polysaccharides of Penicillium and Aspergillus species.

Aspergillus and Penicillium species produce extracellular polysaccharides which are immunologically active. Methyl beta-D-galactofuranoside interferes with the reaction between the polysaccharide antigens and the antibodies raised in rabbits. Of the different interlinked dimers of beta-D-galactofuranosides (1----2; 1----3; 1----5; 1----6) the (1----5) interlinked beta-D-galactofuranoside gave the highest inhibition. An increasing inhibitory effect of di-, tri-, tetra-, penta-, hexa-, and heptamer of (1----5) interlinked beta-D-galactofuranosides was observed. It was noticed that the penta-, hexa- and heptamer of (1----5) interlinked beta-D-galactofuranosides were able to link antibodies raised against the extracellular polysaccharides produced by Penicillium species. The tetramer molecule was able to neutralize the binding of antibodies, which are naturally present in human sera, to the polysaccharides produced by Penicillium and Aspergillus species.

Antibodies, Fungal↗
PubMed1987

Fibrinogen lysine residue A alpha 157 plays a crucial role in the fibrin-induced acceleration of plasminogen activation, catalyzed by tissue-type plasminogen activator.

In previous studies, we have shown that the stretch 148-197 of the fibrinogen A alpha chain plays a crucial role in the acceleration of the tissue-type plasminogen activator (t-PA)-catalyzed plasminogen activation. In this study we have synthesized parts of A alpha 148-197 and analogues thereof. We found that the peptides with sequences identical with A alpha 148-161 and A alpha 149-161 of human fibrinogen accelerate the plasminogen activation by t-PA, whereas the corresponding peptides in which lysine residues A alpha 157 had been replaced by valine or arginine had no accelerating capacity. Furthermore, succinylation of the lysine residue(s) in the synthesized peptides A alpha 148-161 and A alpha 149-161 leads to loss of accelerating action. These findings show that lysine residue A alpha 157 is crucial for the accelerating action of fibrin on the t-PA-catalyzed plasminogen activation.

Amino Acids↗
PubMed1986

gamma-Endorphin and schizophrenia: amino acid composition of gamma-endorphin and nucleotide sequence of gamma-endorphin cDNA from pituitary glands of schizophrenic patients.

The possibility has been mentioned that a change in the structure is responsible for the deviant behavioral activity of gamma-endorphin in extracts of postmortem brain and pituitary gland samples of schizophrenic patients. This paper describes the investigation of this possibility by means of: amino acid composition analysis of alpha- and gamma-endorphin isolated from a pituitary gland of a schizophrenic patient; and nucleotide sequence analysis of the gamma-endorphin coding region of pro-opiomelanocortin (POMC) mRNA from two other pituitary glands, using the primer extension method. Both methods require no more than a single pituitary to obtain reliable results. alpha- and gamma-endorphin were isolated from an acid extract by gel filtration and two subsequent HPLC steps. In addition, the gamma-endorphin region of beta-endorphin was analyzed by enzymatic cleavage of beta-endorphin and isolation of the resulting fragment. Single-stranded gamma-endorphin cDNA was synthesized by reverse transcriptase using total cellular pituitary RNA and a 5' 32P-labeled oligodeoxyribonucleotide primer (20-mer) hybridizing close to the gamma-endorphin coding region of POMC mRNA. Single-stranded cDNA was digested with restriction enzyme HaeIII which generated a 148 nucleotides long radioactive cDNA fragment containing the gamma-endorphin cDNA sequence. The sequence of the 148 nucleotides fragment was determined. Neither the amino acid composition analysis nor the amino acid sequence derived from the cDNA nucleotide sequence revealed differences between schizophrenics and controls. Thus, no evidence was found for changes in the amino acid sequence of pituitary gamma-endorphin in these analyses, which include 3 cases of schizophrenia.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1986

A human gastric carcinoma contains a single mutated and an amplified normal allele of the Ki-ras oncogene.

The DNA from various human tumors and tumor cell lines was screened for the presence of mutated ras oncogenes with synthetic oligonucleotide probes, as well as with the NIH/3T3 cell transfection assay. Among the various mutations found we discovered two novel Ki-ras mutations in codon 12: gly to ala and gly to ser. A gastric carcinoma was found to possess a single mutated Ki-ras allele (gly-12 to ser), as well as a 30-50 fold amplified normal allele. This implies that two activating steps must have occurred in this malignancy.

Alleles↗
PubMed1986

Characterization of the promoter of the large ribosomal RNA gene in yeast mitochondria and separation of mitochondrial RNA polymerase into two different functional components.

We have characterized a DNA sequence that functions in recognition of the promoter of the mitochondrial large rRNA gene by the yeast mtRNA polymerase. Promoter-containing DNA fragments were mutagenized and used as templates to study initiation of transcription in vitro with a partially purified mtRNA polymerase preparation. Deletion mutants, in which increasing stretches of DNA were removed from regions flanking the promoter, define a short area essential for correct initiation of transcription. It virtually coincides with a highly conserved stretch of nine nucleotides that is found immediately upstream of all transcriptional start sites described thus far. Two different point mutations within this nonanucleotide sequence drastically reduce promoter function. Conversely a single point mutation that results in the formation of a nonanucleotide sequence 99 nucleotides upstream of the large rRNA gene leads to a new, efficient transcription initiation site. MtRNA polymerase can be resolved into two different components by chromatography on Blue Sepharose: one retaining the capacity to synthesize RNA, the other conferring the correct specificity of initiation to the catalytic component.

Base Sequence↗
PubMed1986

Characterization of the gene for the microbody (glycosomal) triosephosphate isomerase of Trypanosoma brucei.

To determine how microbody enzymes enter microbodies, we are studying the genes for glycosomal (microbody) enzymes in Trypanosoma brucei. Here we present our results for triosephosphate isomerase (TIM), which is found exclusively in the glycosome. We found a single TIM gene without introns, having one major polyadenylated transcript of 1500 nucleotides with a long untranslated tail of approximately 600 nucleotides. By a novel method, suitable for low abundance transcripts, we demonstrate that TIM mRNA contains the 35-nucleotide leader sequence (mini-exon) also found on several other trypanosome mRNAs. The TIM gene and a DNA segment of at least 6 kbp upstream of the gene are transcribed at an equal rate in isolated nuclei, suggesting that the gene is part of a much larger transcription unit. The predicted protein is of the same size as TIMs from other organisms and shares approximately 50% amino acid homology with other eukaryote TIMs, somewhat less with prokaryote TIMs. Trypanosome TIM is the most basic of all TIMs sequenced thus far. This is, in part, due to the presence of two clusters of positively charged residues in the molecule which may act as a signal for entry into glycosomes.

Amino Acid Sequence↗
PubMed1985

Topogenesis of microbody enzymes: a sequence comparison of the genes for the glycosomal (microbody) and cytosolic phosphoglycerate kinases of Trypanosoma brucei.

To determine how microbody enzymes enter microbodies, we are studying the genes for cytosolic and glycosomal (microbody) isoenzymes in Trypanosoma brucei. We have found three genes (A, B and C) coding for phosphoglycerate kinase (PGK) in a tandem array in T. brucei. Gene B codes for the cytosolic and gene C for the glycosomal isoenzyme. Genes B and C are 95% homologous, and the predicted protein sequences share approximately 45% amino acid homology with other eukaryote PGKs. The microbody isoenzyme differs from the cytosolic form and other PGKs in two respects: a high positive charge and a carboxy-terminal extension of 20 amino acids. Our results show that few alterations are required to redirect a protein from cytosol to microbody. From a comparison of our results with the unpublished data for three other glycosomal glycolytic enzymes we infer that the high positive charge represents the major topogenic signal for uptake of proteins into glycosomes.

Amino Acid Sequence↗
PubMed1984

Three different mutations in codon 61 of the human N-ras gene detected by synthetic oligonucleotide hybridization.

The activation of ras genes in naturally occurring tumors has, thus far, been found to be due to mutations in codon 12 or 61 resulting in single amino acid substitutions. We have used highly labeled synthetic oligonucleotides to detect mutations in these codons and to determine the exact position of the mutation. Using this approach we have found three different mutations in codon 61 of the N-ras gene of various human tumor cell lines. In the fibrosarcoma line HT1080 the first nucleotide of the codon is mutated; in the promyelocytic line HL60 the second and in the rhabdomyosarcoma line RD301 the third nucleotide. For RD301 this implies that the normal glutamine residue at position 61 is replaced by histidine. In addition to the mutated N-ras gene the three cell lines have a normal N-ras gene which is indicative of the dominant character of the mutations.

Base Sequence↗
PubMed1984

Polymer supported DNA synthesis using hydroxybenzotriazole activated phosphotriester intermediates.

Phosphorylation of N-acyl-5'-O-DMTr-d-nucleosides, or similarly protected DNA-dimers having a free 3'-OH group, with 2-chlorophenyl-0,0-bis(1-benzotriazolyl)phosphate affords reactive 3'-phosphotriester derivatives. The latter intermediates can be used, without further purification, for the synthesis of DNA-fragments on the controlled pore glass/long chain alkylamine support. Further, 2-cyano-1,1-dimethylethoxy dichlorophosphine proved to be very suitable for the preparation of 5'-phosphorylated DNA-fragments on the same type of solid support.

Chromatography, High Pressure Liquid↗
PubMed1984

Gene A protein cleavage of recombinant plasmids containing the phi X174 replication origin.

Synthetic oligonucleotides, DNA ligase and DNA polymerase were used to construct double-stranded DNA fragments homologous to the first 25, 27 or 30 b.p. of the origin of replication of bacteriophage phi X174 (nucleotides 4299-4328 of the phi X174 DNA sequence). The double-stranded DNA fragments were cloned into the unique SmaI or HindIII restriction sites in the kanamycin-resistance gene of pACYC177 (AmpR, KmR). Recombinant plasmids were picked up by colony hybridization. DNA sequencing showed that not only recombinant plasmids with the expected insert were formed, but also recombinant plasmids with a shorter insert. Recombinant plasmids with an insert homologous to the first 24, 25, 26, 27, 28 or all 30 b.p. of the phi X174 origin region were thus obtained. Supercoiled plasmids containing a sequence homologous to the first 27, 28 or 30 b.p. of the phi X174 origin region are nicked by the phi X174 gene A protein. However, the other supercoiled plasmids are not nicked by the phi X174 gene A protein. These results show that the first 27 b.p. of the phi X174 origin region are sufficient as well as required for the initiation step in phi X174 RF DNA replication, i.e. the cleavage by gene A protein.

Bacteriophage phi X 174↗