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Biomedical subjects

M Adam

Publications and source records attributed to M Adam.

At least 73 records · Page 4Linked to original sources
PubMed1994

Anaplastic Wilms' tumour, a subtype displaying poor prognosis, harbours p53 gene mutations.

The genetics of Wilms' tumour (WT), a paediatric malignancy of the kidney, is complex. Inactivation of the tumour suppressor gene, WT1, is associated with tumour aetiology in approximately 10-15% of WTs. Chromosome 17p changes have been noted in cytogenetic studies of WTs, prompting us to screen 140 WTs for p53 mutations. When histopathology reports were available, p53 mutations were present in eight of eleven anaplastic WTs, a tumour subtype associated with poor prognosis. Amplification of MDM2, a gene whose product binds and sequesters p53, was excluded. Our results indicate that p53 alterations provide a molecular marker for anaplastic WTs.

Alleles↗
PubMed1994

Design and validation of a new immunoassay for soluble forms of thrombomodulin and studies on plasma.

Thrombomodulin (TM), purified from human placental homogeneate by affinity chromatography on DIP-Thrombin agarose, was used to develop monoclonal antibodies (MAbs). Two of them, 3E2 and 24FM (both IgG1, K), which were not calcium-dependent, were found convenient for developing a two-site enzyme immunoassay. Testing of recombinant and truncated forms of TM26 demonstrated that the species containing the amino terminus including the lectin-like domain and the epidermal growth factor (EGF)-like domains 1-4 were fully measured. The working range was from 2 to 100 ng/ml with a detection threshold of 2 ng/ml. Intraassay and interassay reproducibilities were, respectively, below 7.4% and 8.6%, whereas recovery of purified TM was between 88 and 114% in plasma. Mean plasma concentration was 42.1 (+/- 11.3) ng/ml (males 51.8 +/- 7.9 ng/ml, females 34.8 +/- 7.8 ng/ml) and it was established on 62 normal individuals between the ages of 21 and 55 (28 males and 34 females). This new assay is a convenient tool for measuring plasma TM and establishing its diagnostic and predictive value in diseases associated to endothelial damage.

Adult↗
PubMed1994

Patient perceptions of the experience of electrophysiologic studies.

This descriptive study explored perceptions, feelings and attitudes related to electrophysiologic studies (EPS). Structured one hour taped interviews were conducted with 11 participants and data was subjected to qualitative analysis. Powerlessness, anticipation and total exhaustion were the categories identified from the data. Overall, participants generally perceived their EPS as a negative experience and illustrated this with words like invasion, horrible, uncomfortable, etc. Anxiety was predominant throughout the entire experience. Nurses are in an ideal position to impact these negative perceptions by helping patients incorporate the threatening nature of EPS into a cognitive plan, thus reducing anxiety. Strategies and interventions to help patients cope with this aversive event are offered as well as suggestions for future research.

Aged↗
PubMed1994

Transgenic mice harboring Aujeszky's disease virus gD gene.

Plasmid pMLP10 gp50.5 (gD) (Eloit et al., 1990) provided the sequence to integrate. The construct has been injected into the male pronucleus of one-cell mouse embryos (CBA/C5B1). A total of 1,567 microinjected embryos were transferred into the oviduct of pseudopregnant females (Hogan et al., 1986). PCR revealed that 3 out of 10 mice were born with an integrated construct; among them, 2 mice have integrated the construct in their gonads because 20 out of 107 (18.7%) of their offspring were also transgenic. This low percentage could be explained by germline mosaicism and/or differential mortality between transgenic and non-transgenic embryos.

Animals↗
PubMed1993

Cloning and expression of a cDNA for the human prostaglandin E receptor EP1 subtype.

A functional cDNA clone coding for the human prostaglandin E receptor EP1 subtype has been isolated from a human erythroleukemia cell cDNA library probed by low-stringency hybridization using a polymerase chain reaction fragment of the human thromboxane receptor. The human EP1 receptor is comprised of 402 amino acids with a predicted molecular mass of 41,858 and has the topography common to all G-protein-coupled receptors with seven predicted transmembrane spanning domains. Prostaglandin (PG) E2 challenge of Xenopus oocytes injected with EP1 cDNA resulted in an increase in intracellular Ca2+. In addition, the rank order of potency for prostaglandins in competition for [3H]PGE2 specific binding to membranes prepared from EP1 cDNA transfected COS cells was PGE2 > PGE1 > PGF2 alpha > PGD2. Furthermore, the EP1 receptor-selective antagonists AH 6809 and SC19220 were more potent than the EP2 receptor-selective agonist butaprost in these competition binding assays. In summary, therefore, we have cloned the human EP1 receptor subtype which is functionally coupled to an increase in intracellular Ca2+.

Amino Acid Sequence↗
PubMed1993

Cloning, expression and mutational analysis of SH-PTP2, human protein-tyrosine phosphatase.

A human cDNA clone encoding a nonreceptor protein-tyrosine-phosphatase (PTP) has been isolated and sequenced. The 2.1 kilobase pair cDNA encodes for a 593 amino acid protein that contains a single tyrosine phosphatase catalytic domain at the C-terminus. At the N-terminus the protein has two adjacent copies of Src homology region (SH2 domain) which show 61% and 73% identity at the amino acid level to the SH2 domains of the human PTP1C and Drosophila corkscrew protein, respectively. The overall homology between SH-PTP2 and PTP1C or to corkscrew protein is 58%. When this protein (or its catalytic domain) was expressed in E. coli as a glutathione-S-transferase fusion protein tyrosine-phosphatase activity was detected in bacterial cell extracts. Site-directed mutation made at the conserved cysteine (459) residue to serine within the highly conserved VHCXAGXXR sequence in the PTP catalytic domain resulted in complete loss of enzymatic activity demonstrating the importance of this cysteine residue in catalysis. Northern blot analysis showed that SH-PTP2 is expressed as a 6.5 kilobase mRNA in a number of fetal and adult human tissues and cell lines. The highest levels of its mRNA were detected in fetal brain and in adult heart tissue. The identification of SH-PTP2 along with PTP1C and corkscrew protein suggest that there exist a family of nonreceptor PTP containing SH2-domain which will participate in specific signal transduction pathways involving tyrosine phosphorylation-dephosphorylation.

Amino Acid Sequence↗
PubMed1993

Enantioselective activation of the peroxisome proliferator-activated receptor.

A cell-based transactivation assay was established using the mouse full-length peroxisome proliferator-activated receptor (PPAR) cDNA sequence and the positive peroxisome proliferator-responsive regulatory element (-578 to -553) of the rat acyl-CoA oxidase gene promoter. Activation of the reporter plasmid was dependent on co-transfection of the full-length PPAR cDNA, and the response was greatly stimulated, up to 100-fold, by peroxisome proliferators such as Wy-14,643 ([4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio] acetic acid), nafenopin (2-methyl-2[p-(1,2,3,4-tetrahydro-1-naphthyl)phenoxy]-propionic acid), and clofibric acid (2-([p]-chlorophenoxy)-2-methylpropionic acid). Activation of the reporter plasmid promoter by the full-length PPAR cDNA also occurred at peroxisomal proliferator concentrations 40 times lower than that required for similar stimulation by a glucocorticoid-PPAR chimeric receptor. By using the stereoisomers of MK-571 ((+-)-3-(((3-(2-(7-chloro-2-quinolinyl)ethenyl)-phenyl)((3- (dimethylamino)-3-oxopropyl)-thio)methyl)-thio)propanoic acid), a potent leukotriene D4 receptor antagonist, we could show enantioselective activation of PPAR. The use of this compound in mice results in peroxisome proliferation; however, nearly all of the peroxisome proliferating activity can be attributed to the S enantiomer. Our results show a similar enantiomeric discrimination in PPAR activation of the reporter plasmid promoter, where again most of the activity can be attributed to the S enantiomer. The equivalent activities of these stereoisomers both in vivo and in the PPAR transactivation assay strongly implicate PPAR as a major component of the peroxisome proliferating mechanism in rodents.

Acyl-CoA Oxidase↗
PubMed1993

Poly(HEMA)-collagen composite as a biomaterial for hard tissue replacement.

This article briefly reviews the possibilities for hard tissue replacement with a new biomaterial. The basic differences found experimentally for polymer (HEMA) and collagen composite at the biological environment are stressed. The influence of the collagen distribution and matrix porosity of composite material on biodegradation is also discussed.

Animals↗
PubMed1993

A novel genetic thrombocytopenia (Paris-Trousseau) associated with platelet inclusions, dysmegakaryopoiesis and chromosome deletion AT 11q23.

We report a novel case of hereditary thrombocytopenia. A chronic thrombocytopenia was noted in a woman with mild hemorrhagic complications as well as in her very young son. A platelet fraction contained giant granules stained in red on blood smears. The number of bone marrow megakaryocytes was increased with many micromegakaryocytes. Since the platelet life span was normal, these results indicated an ineffective platelet production. A constitutional cytogenetic abnormality was detected in the two patients: a deletion of the long arm of chromosome 11. The association of these abnormalities constitute a new disorder: this never described cytological entity is a valuable model for exploring the role of some genes involved in the regulation of thrombopoiesis.

Adult↗
PubMed1993

[Morphological studies of Babesia divergens during continuous transfer in Meriones unguiculatus].

A strain of Babesia divergens was propagated by inoculation of 1.5 x 10(7) parasitized erythrocytes in 30 passages under same conditions on altogether 150 jirds. The developmental stages of Babesia divergens revealed pleomorphism in the erythrocytes of the jird. Single parasites were observed as being pyriform, globular, budding, ring-like or amoebid. The shape of dividing parasites varied between the spherical and the pyriform. The stages in the erythrocytes were localized predominantly intermedia. The reduction of the number of dividing forms and the increase of single forms occurred with increasing numbers of passages. Length and breadth of double pyriforms increased by approximately 20%.

Animals↗
PubMed1992

Crystalline enzyme kinetics: activity of the Streptomyces R61 D-alanyl-D-alanine peptidase.

The specificity constant, kcat/Km, for the hydrolysis of hippuryl-mercaptoacetate by crystals of the Streptomyces R61 D-D peptidase was measured by reaction of the thiol produced with 4,4'-dithiodipyridine. The values of kcat/Km for the crystal and in solution were the same (within experimental error). A novel method for treating the lag in the progress curves was developed.

Carboxypeptidases↗
PubMed1992

Importance of the His-298 residue in the catalytic mechanism of the Streptomyces R61 extracellular DD-peptidase.

Among the active-site-serine penicillin-recognizing proteins, the Streptomyces R61 extracellular DD-peptidase is the only one to have a His-Thr-Gly sequence [instead of Lys-Thr(Ser)-Gly] in 'box' VII. The His residue was replaced by Gln or Lys. Both mutations induced a marked decrease in the rates of both tripeptide substrate hydrolysis and acylation by benzylpenicillin and cephalosporin C. The rate of hydrolysis of the thioester hippuryl thioglycollate was less affected. The most striking result was the disproportionate loss of transpeptidation properties by both mutants, indicating an important role of His-298 in this reaction. We believe that this result represents the first modification of a DD-peptidase leading to a specific decrease of the transpeptidation-to-hydrolysis ratio.

Amino Acid Sequence↗
PubMed1992

Implantation of p(HEMA)-collagen composite into bone.

The replacement of bone defects is very important in clinical practice. This study compares biological properties of poly(2-hydroxyethyl methacrylate)-collagen composite with those exhibited by pure p(HEMA), an insoluble fraction of calf skin collagen (ISC-40) and demineralized bone matrix after implantation into pig or dog femurs. The levels of biodegradation or destruction of implants and healing of bone defects were studied using X-ray photography, histology and enzyme histochemistry. The results indicated a significant effect of collagen on biological destruction of the p(HEMA)-composite implants; even a minute amount of collagen influences this process dramatically. A stimulatory action of collagen on new bone formation may be of importance in bone defect healing.

Animals↗
PubMed1992

Autologous peripheral blood stem cell transplantation after high dose therapy in patients with advanced lymphomas.

Thirty-eight patients with refractory or relapsed non-Hodgkin's lymphoma (19 patients) or Hodgkin's disease (19 patients) were treated with salvage therapy. The peripheral stem cell collection was performed during hematologic recovery after myeloablative chemotherapy. In eight patients with Hodgkin's disease the number of CFU-GM collected was less than 0.5 x 10(4)/kg and these patients were excluded for stem cell transplantation. In the remaining 30 patients, a median of 4 x 10(4) CFU-GM/kg was collected (range 0.8-100 x 10(4)/kg) by three leukaphereses in 25 patients and six to 11 leukaphereses in five patients. Conditioning regimens were CBV (eight), BEAM (six), BEAC (10) and cyclophosphamide + total body irradiation (TBI) (six). Without TBI, the mean time for reaching a granulocyte count greater than 0.5 x 10(9)/l was 18 days and for a platelet count greater than 50 x 10(9)/l was 19 days in 23 out of 24 patients. With TBI, in five patients the mean time for reaching a granulocyte count greater tahn 0.5 x 10(9)/l was 37 days and for a platelet count greater than 50 x 10(9)/l was greater than 100 days. Complications were minor. There was only one toxic death. The outcome in these patients was similar to that observed in patients who received autologous bone marrow transplantation for advanced lymphomas. In conclusion, we observed good hematologic recovery except when TBI was used in the conditioning regimen.

Adolescent↗
PubMed1992

Identification of amino acid residues of 5-lipoxygenase-activating protein essential for the binding of leukotriene biosynthesis inhibitors.

5-Lipoxygenase-activating protein (FLAP) is specifically labeled by [125I]L-669,083 and [125I]L-691,678, photoaffinity analogues of two classes of potent leukotriene biosynthesis inhibitors. Because human FLAP contains only a single tryptophan residue at position 72 and two internal methionine residues at positions 89 and 125, we have used reagents that specifically cleave at these residues, in conjunction with antipeptide antisera, to localize the site of attachment of the photoaffinity ligands. Immunoprecipitation of specifically labeled peptide fragments after digestion of photoaffinity-labeled FLAP by iodosobenzoic acid at 72Trp demonstrates that the inhibitors bind to FLAP amino-terminal to this residue. This finding is consistent with similar immunoprecipitation studies after digestion at methionine residues using cyanogen bromide. These findings localize the site of attachment of the inhibitors to a region of FLAP that includes the hydrophilic loop between the proposed first and second transmembrane regions. Based on these findings, site-directed mutagenesis of human FLAP was performed to define key amino acids involved in inhibitor binding. Using a radioligand binding assay, analysis of mutants of human FLAP expressed in COS-7 cells demonstrates that a number of residues in the amino-terminal half of the first hydrophilic loop of the protein can be deleted without significantly affecting inhibitor binding. In contrast, no inhibitor binding was detectable with mutants in which amino acid residues in the carboxyl-terminal half of this loop were deleted. Furthermore, a point mutation of 62Asp to asparagine results in a mutant with dramatically reduced affinity for inhibitors. This loss of affinity was not displayed by a mutant in which 62Asp was mutated to a glutamate residue, suggesting that a negative charge associated with residue 62 may be critical for inhibitor binding. The roles that amino acid residues in the carboxyl-terminal half of the first hydrophilic loop of FLAP may play in the binding of leukotriene biosynthesis inhibitors are currently under investigation.

5-Lipoxygenase-Activating Proteins↗
PubMed1991

The nucleotide sequence of a voltage-gated chloride channel from the electric organ of Torpedo californica.

The cDNA encoding the voltage-gated chloride channel from the electric organ of Torpedo californica has been isolated and sequenced. The 2.7 kilobase pair cDNA encodes an 810 amino acid polypeptide which is highly homologous at both the DNA (97%) and amino acid (97%) levels to the voltage-gated chloride channel from the electric organ of T. marmorata. The majority of the 24 amino acid differences between the T. californica and T. marmorata voltage-gated chloride channels are clustered in two putative cytoplasmic domains with six differences located between residues 10-92 and 14 differences occurring between residues 576 to 708. Only one amino acid difference occurs in one of the predicted transmembrane domains. The most dramatic difference is an insertion of Asp-Val-Pro-Gly in a large cytoplasmic domain at amino acid residue 627 of the T. californica channel.

Amino Acid Sequence↗
PubMed1991

Accumulation of acyl-enzyme in DD-peptidase-catalysed reactions with analogues of peptide substrates.

Thioester substrates can be used to study the hydrolysis and transfer reactions catalysed by beta-lactamases and DD-peptidases. With the latter enzymes, accumulation of the acyl-enzyme can be detected directly. The efficiency of various amines as acceptor substrates was in excellent agreement with previous results obtained with peptide substrates of the DD-peptidases. The results indicated the presence of a specific binding site for the acceptor substrates. Although most of the results agreed well with a simple partition model, more elaborate hypotheses will be needed to account for all the data presented.

Acylation↗